3D printable 2x4 cross connector: joins two 2x4s on edge crossing like a plus, one stacked on the other (STL, STEP) — dimension sheet
Source: Xem Studio, https://xemstudio.com/objects/2x4-cross-block-connector/  (sheet CC BY 4.0; files Xem Studio Design License, https://xemstudio.com/license/)
Basis: 2x4 dressed (dry) size 1-1/2 × 3-1/2 in (38.1 × 88.9 mm) per DOC PS 20 American Softwood Lumber Standard; 1.4 mm sliding clearance is Xem's FDM default for this part.
Catalog version: 2026-10-20

Overall (mm): length 55.5, width 55.5, height 90.0
- Both boards stand on edge (the 1-1/2 in side is the width). The block slides down over the lower board and the upper board drops into the top slot at 90°, so the stack is about 7 in to the top of the upper board.
- No cutting or notching of the lumber. Add a screw through a wall into each board if the joint must not lift apart.
- Slots are 39.5 mm for a 38.1 mm board. Rough-sawn, wet or swollen 2x4s can run thicker: test-fit one block first.
- Print upright as modelled, 4 or more walls, 20 % or more infill, PETG or ABS outdoors. No supports: the lower slot's 39.5 mm ceiling bridges.

feature  size mm  fits
block  55.5 × 55.5 × 90  —
lower slot (opens down, along X)  39.5 wide × 40 deep  2x4 on edge, 38.1 thick
upper slot (opens up, along Y)  39.5 wide × 40 deep  2x4 on edge, 38.1 thick
walls / web  8 / 10  —
lead-in chamfer  1.5  —

Files elsewhere (not hosted by Xem Studio; license as stated by the publisher):
- NIST / ALSC: Voluntary Product Standard PS 20-25, American Softwood Lumber Standard — web — Publisher's page; dimensions are facts — https://www.nist.gov/document/ps-20-25-final
- American Wood Council: Weights and Measurement: nominal vs actual lumber sizes — web — Publisher's page; dimensions are facts — https://awc.org/weights-and-measurement

Free files (Xem Studio Design License, Xem Studio; STEP + STL, 1 parts): https://xemstudio.com/files/hardware/2x4-cross-block-connector/index.json
API: https://xemstudio.com/api/geometry?object=2x4-cross-block-connector