Hardware Buying Guide
LEGO Technic Pin Guide for Mosaics
Connector pins are one of the most misunderstood parts in LEGO mosaic builds. The short version: they're optional for most builds, mandatory for one specific style (LEGO Art thick panels), and the wrong solution for everything else. This guide covers exactly when you need pins, which part to buy, how many, and where.
Do you actually need pins?
Pins are required only for one specific baseplate strategy. For all other strategies, pins are not part of the build.
Skip pins if you're using flat baseplates
Webrick 48×48 #4186, 32×32 #3811, or 16×16 #91405 plates have no Technic holes on the sides. There is nothing for a pin to attach to. Skip the pin order entirely — use a backing board with double-sided tape instead.
Buy pins if you're using LEGO Art 16×16 thick panels
LEGO #65803 (Technic Brick 16×16×1⅓ with Holes) is the only mosaic baseplate that uses pins. Each panel has 16 Technic holes on each edge. Pins join the panels into a self-supporting modular structure — the same construction LEGO Art sets use.
Buy a small handful as repair stock
Even if you don't need pins for the build, a small bag (10–20 pins) is handy for any future LEGO Technic project or repair. Approx $2–5 from Webrick or BrickLink.
The Technic Friction Pin (LEGO #2780)
This is the specific part used for LEGO Art mosaic construction.
- Part number: LEGO #2780 (also "Technic, Pin with Friction Ridges Lengthwise WITH Center Slots")
- Length: 2 modules (16mm total, 8mm per side after inserting)
- Color: Black (standard) — color is hidden once panels are joined
- Function: Friction ridges grip both panel holes when inserted halfway through, locking adjacent panels together
- NOT to confuse with: Pin without friction (#3673, smooth) — smooth pins won't hold the panels together rigidly
Pin counts by mosaic size
Plan roughly 4 pins per inter-module edge. Adjacent 16×16 panels share an edge with 16 Technic holes — 4 pins is typical for a secure connection without using every hole.
| Mosaic size | 16×16 panels needed | Inter-module edges | Recommended pin count | Approx cost (PAB / Webrick) |
|---|---|---|---|---|
| 48×48 | 9 (3×3) | 12 | ~36 pins | $7 / ~¥15 |
| 48×64 | 12 (3×4) | 17 | ~48 pins | $10 / ~¥19 |
| 48×96 | 18 (3×6) | 27 | ~72 pins | $14 / ~¥29 |
| 64×64 | 16 (4×4) | 24 | ~64 pins | $13 / ~¥26 |
| 64×96 | 24 (4×6) | 38 | ~96 pins | $19 / ~¥38 |
| 96×96 | 36 (6×6) | 60 | ~144 pins | $29 / ~¥58 |
| 96×144 | 54 (6×9) | 93 | ~216 pins | $43 / ~¥86 |
Order 10% extra. Pins are cheap, you will lose some on the floor, and running short mid-build is annoying.
Where to buy pins
LEGO Pick-a-Brick
LEGO PAB: search part #2780. Approximately $0.20 each. Official quality, shipped with your other PAB order — no extra shipping if you're already ordering bricks.
BrickLink — Cheapest for bulk
BrickLink: search "Technic Pin with Friction Ridges Lengthwise WITH Center Slots". $0.05–0.10 per pin in bulk. Multiple sellers offer 50+ pin bags for $3–5. Best price if you're already ordering bricks here.
Webrick — Compatible alternative
Webrick stocks compatible pins. ~¥0.40 (~$0.05) each. Best if you're ordering Webrick baseplates and pieces in the same shipment.
Amazon — Fastest
Search LEGO Technic friction pin 50 pack on Amazon. Bulk packs of 100–200 LEGO-compatible pins for $5–10. Prime shipping. Quality varies — check reviews for "tight friction" before buying generic brands.
Common pin mistakes
Buying pins when you don't need them
The most common mistake. If you're using flat Webrick baseplates, you don't need pins. They literally cannot attach to anything. Refer to the baseplate buying guide for which strategy you're on.
Buying the wrong pin type
LEGO has many pin variants. The mosaic panel pin is specifically #2780 friction pin. Smooth pins (#3673) and 3-length pins (#32556) will fit but won't hold the panels together with enough friction.
Inserting pins fully into one panel before joining
Each pin should be pushed halfway through — 1 module deep into each adjacent panel. If you push a pin fully into one panel first, you can't connect it to the next panel. Practice on a scrap pair before doing the real build.
Over-counting pins
You don't need to fill every Technic hole on each edge. 4 pins per edge is more than enough for a wall-mounted display piece. Filling all 16 holes per edge wastes pins and makes future disassembly painful.
FAQ
Do I need pins for a 48×48 LEGO mosaic?
Only if you're using LEGO Art-style 16×16 thick panels (#65803). For flat baseplate strategies (single 48×48 Webrick #4186 or 9× 16×16 plates), pins are not used — mount the baseplates on a backing board with adhesive instead.
What LEGO part number do I need for mosaic connector pins?
LEGO Part #2780, the Technic Friction Pin with Center Slots. Length: 2 modules. Color: black. Specifically the friction-ridged version — smooth pins (#3673) won't hold panels together rigidly.
How many pins for a 96×96 mosaic?
Approximately 144 pins (4 pins per inter-module edge × 60 edges). Order 160 to allow for 10% loss/spares. Cost: ~$29 from LEGO PAB or ~¥58 (~$8) from Webrick.
Can I use any LEGO Technic pin instead of #2780?
No. The friction ridges on #2780 are what holds adjacent panels rigid. Smooth pins (#3673), longer pins (#32556), or axle-pins (#43093) either won't fit or won't grip with enough friction for a wall-mounted display piece.
Are LEGO-compatible pins as good as official LEGO?
Generally yes for mosaic use. The pin is hidden inside the panels — quality only matters in terms of friction grip. Webrick and reputable Amazon brands work fine. Avoid the cheapest unbranded options — loose pins make panels rattle.
What happens if I run out of pins mid-build?
The panels are joined sequentially, so a partial pin shortage just delays completion until you can order more. The half-finished section won't fall apart — gravity and the partial pinning are sufficient to keep things in place on a flat surface. Don't hang the piece until all pins are in.
Related hardware guides
- LEGO Baseplate Buying Guide — which baseplate strategy you should use (most users don't need pins)
- LEGO Mosaic Backing Board Guide — the actual structural alternative to pins for flat-baseplate builds
- LEGO Mosaic Frame Guide — frame depth, IKEA Ribba sizing, wall-mount hardware
- Full Baseplate & Pins Sourcing Hub — original combined guide