Printed terrain that stores in a loose pile is terrain that chips, tangles, and takes 20 minutes to sort before a game. Magnets solve this. A magnetised terrain set locks into foam trays or stacks in boxes without pieces shifting during transport, and the individual pieces connect to each other and to a magnetic play surface with a positive click rather than a hesitant nudge.

The installation process is not complicated, but it has one rule that bites almost every hobbyist the first time they try it, and breaking that rule means drilling out incorrectly installed magnets and starting again. This article covers the right magnet sizes, the right installation methods, and the polarity rule that prevents that particular frustration.

Why magnets beat clips for serious terrain users

OpenLOCK clips and similar interlock systems work well for a dungeon set that stays on the table. They are fast to assemble and they lock positively. But they impose a design constraint: every piece in the set must use the same clip standard, and the clip geometry is visible on the underside of every base.

Magnets are more flexible. They work with any base geometry, they do not require a specific clip footprint, and they do not show unless the underside of the piece is examined closely. A piece with a well-installed magnet is indistinguishable from an unmodified piece from the front. And a magnetised set stacks vertically: tower segments lock one on top of another, wall sections connect side to side, and terrain pieces sit flat against a steel-underlaid gaming board without moving.

The trade-off is a one-time cost per magnet (small, in bulk) and a one-time installation effort per piece. For a permanent set, that trade-off is worth making.

Magnet sizes for tabletop terrain

Neodymium disc magnets are the right type for terrain work. Flat discs sized to fit in a drilled or printed pocket. The relevant dimensions are diameter and height.

3 mm diameter, 1.5 mm or 2 mm height. The smallest useful size. Right for edge-locking small tiles to each other, for holding scenic figures to a base (magnet under the base, steel washer in the foam tray), and for the fine interlock on thin wall sections. Strong enough to hold a paired piece against gravity at short range; not strong enough to lift a heavy tower segment.

5 mm diameter, 2 mm height. The workhorse size. Right for mid-weight terrain pieces: standard wall sections, door frames, floor-to-wall connections. The step up in pull from the 3 mm is noticeable. Most dungeon tile sets are well served by 5 mm magnets at every joining face.

6 mm diameter, 3 mm height. For heavy pieces: gate sections, tower bases, large centrepieces. The pull is strong enough to lift a paired piece when held at arm’s length. This is overkill for most scatter terrain and the right answer for anything structural.

10 mm diameter. Overkill for tabletop terrain in almost all cases. Reserved for very heavy display bases and pieces that need to hold weight against significant force. Most terrain projects never reach this size.

The note on height: a shorter magnet in a larger diameter is often stronger than a taller magnet at a smaller diameter, because the field area increases faster than the depth. For terrain, prioritise diameter over height once the pocket depth permits.

Magnet grade

Neodymium magnets are graded N35 through N52, where a higher number means stronger pull per unit volume. For terrain, the sweet spot is N42 or N48.

N52 is the strongest grade available in consumer sizes and is tempting but has a drawback: it is more brittle than lower grades and will chip or crack if two N52 magnets snap together hard. For terrain that gets handled at a gaming table, that brittleness is a real failure mode.

N42 is the practical standard. It is strong enough for all the terrain sizes listed above, widely available, and durable enough to survive gaming-table handling. N48 gives a meaningful step up over N42 and is worth sourcing for the 6 mm pieces where you want confident joining force.

For sourcing: KJ Magnetics, Magnetic Trader, and Amazon bulk packs are all reliable. Hobby suppliers serving the scale modelling and wargaming markets stock the common terrain sizes and grade the magnets correctly. Generic no-brand bulk magnets from unspecified sources sometimes run lower than the stated grade; this is rarely a problem for 5 mm and 6 mm terrain work, where the difference is imperceptible, but it is worth knowing about.

The two install methods: pre-printed pocket, or pause-and-drop

There are two ways to get a magnet into a terrain piece.

Pre-printed pocket. The piece is printed with a cylindrical void at the correct location. The magnet drops into the pocket after printing and is secured with cyanoacrylate. This method works for any file you can edit or for files where the creator has included magnet pockets in the design. The pocket must be accurately sized: slightly undersized and the magnet will not seat; slightly oversized and it rattles, and the glue joint is under shear stress rather than tension.

Pause-and-drop. The printer pauses mid-print at a specified layer. The magnet drops into the cavity that has been formed by the printed walls. The printer resumes and the plastic seals over the magnet on the next few layers. The magnet is encapsulated in plastic, which is a stronger and more permanent installation than a glued surface pocket.

Pause-and-drop is the better method when the file supports it. Set the pause two to three layers above the magnet’s height so the cavity is fully formed and the magnet sits below the active print surface. A small dab of cyanoacrylate in the cavity before dropping the magnet is optional; the plastic encapsulation is usually sufficient without it.

The practical limitation of pause-and-drop is that it requires thinking about magnet placement at the slicing stage, before the print starts. Pre-printed pockets work on already-printed pieces, which is the right approach for retroactively magnetising an existing set.

The polarity rule

This is the rule that bites everyone who skips it.

Every magnet installed on a piece must be oriented the same way relative to the surface it faces. If the north pole of every magnet on the bottom of a piece faces down, then the south pole of every magnet on the mating surface of the piece it connects to must also face down (toward that bottom surface). When two terrain pieces are correctly polarised, they attract at every joining point simultaneously. When one magnet is installed backwards, that face repels rather than attracts, and the piece flips when brought near its mate.

The fix for a backwards magnet is to drill it out and install a replacement in the correct orientation. There is no way to invert a glued or encapsulated magnet in place.

The method for avoiding backwards magnets is simple and requires one additional step:

Before installing any magnet, mark one face with a permanent marker. Make this a consistent convention across your entire set: marked face always faces out toward the connection surface (or always faces inward, as long as it is consistent). Use a reference magnet on the bench: a magnet taped to a small card with the correct face labelled. Before every installation, hold the magnet to be installed against the reference magnet and confirm it attracts (matching polarity convention) before it goes into the piece.

Do this for every magnet in the set. Not most of them. Every one.

Glue choice

Cyanoacrylate (super glue) is the correct adhesive for pre-printed pocket magnets. It sets in seconds, works on both plastic and steel, and produces a rigid bond that does not creep under the light tension of repeated magnet engagement.

Specific brands that work well: Loctite Super Glue, Bob Smith Industries BSI-175 (a standard in the hobby community), and Gorilla Super Glue. Any medium-viscosity cyanoacrylate is fine. Thin cyanoacrylate wicks under the magnet and can produce a very clean bond; thick gel cyanoacrylate is easier to apply precisely without running into the cavity.

Avoid:

  • Two-part epoxy. It is overkill, slow to set (5 to 30 minutes depending on type), and the additional curing time is unnecessary when cyanoacrylate sets in 30 seconds.
  • PVA (white glue). Too weak. The shear force of repeated magnet separation will work PVA loose within weeks of regular use.
  • Hot glue. Works in the short term but pops free the first time the terrain piece is left in a warm environment (a car boot in summer, a table near a window). Magnet pockets are exposed to modest heat stress; hot glue is not the right adhesive for this.

How to fix a backwards magnet

Despite the polarity rule and the reference-magnet check, a backwards installation will happen eventually. The fix:

Use a drill bit that matches the magnet diameter. A 3 mm bit for a 3 mm magnet, a 5 mm bit for a 5 mm magnet. Drill carefully into the pocket at low speed, breaking the cyanoacrylate bond. Extract the magnet and the plastic debris with a flat blade. Clean the pocket. Install a replacement magnet in the correct orientation and re-glue.

Do not attempt to place a second magnet on top of the wrong-facing one to invert the field. This creates a weak, unstable installation that will fail on the next impact.

For encapsulated (pause-and-drop) magnets, the process is the same but requires drilling through the printed cap layer before reaching the magnet.

Specific terrain applications

Magnetising bases for figures. A 3 mm magnet under a round or square base, combined with a 3 mm steel washer pressed into the foam tray, keeps figures from falling over during transport. The washer cost is negligible. This is the most commonly described miniature magnetising technique in the hobby community.

Magnetising tower segments for vertical locking. Two tower sections that stack vertically stay locked during play and separate cleanly for storage. 6 mm magnets at the joining face are strong enough to hold the top section in place when lifted by the upper piece. Use the pause-and-drop method for tower segments; the encapsulation is stronger than a surface pocket for pieces that take regular impact.

Magnetising terrain to a play surface. A steel sheet underlaid beneath the gaming board, or steel screwheads set into a plywood board surface, lets terrain pieces with 5 mm base magnets lock to the board itself. The terrain does not shift during play. This is particularly effective for scatter terrain (rocks, barrels, braziers) that would otherwise nudge out of position.

For the broader context of how magnetised terrain fits into a modular set, the how to print modular terrain guide covers the full workflow from file selection through batch printing to storage. For slicer settings that work best when including magnet cavities in your print profiles, the FDM slicer settings article for tabletop terrain covers the full profile. And for printer options that support the pause-and-drop method well, the best 3D printer for terrain guide covers the current field.

Magnets transform a printed terrain collection into a set you can transport in a box, set up in five minutes, and recover fully after a game. The polarity rule is the only one that has a real cost if you skip it. Mark every magnet before it goes in, use a reference on the bench, and the installation is fast and reliable.