Reverse LEGO Part Finder

Identify LEGO Bricks From the Bottom

Can't see the top of your piece? Filter by anti-stud tubes, ribbing, wall height, and groove across the full catalog — no photo required.

Underside Inspector

Step 1: Outer Footprint (Stud Grid)Top/Bottom Dimensions

Step 2: Underside Tube / Anti-Stud StructureWhat's inside the bottom?

Step 3: Tube Count

Step 4: Vertical Wall Height

Step 5: Internal Ribbing

Bottom Edge Groove (Tile Lip)?

Tiny lip for fingernail / separator removal on the bottom edge

Interactive Vector ViewUnderside Diagram

Set a filter to searchFull catalog

Possible Matches

Set at least one filter

Example: footprint 2 × 4, hollow tubes, full brick height → #3001.

How to use it

Identify a brick by its bottom profile — tubes, posts, grooves, and ribbing.

Pick traits

Choose the footprint (2×4, 1×2, Technic beam, etc.).
Select tube structure — hollow tubes, solid posts, tile groove, axle cross.
Set profile height (brick vs plate vs tile) and tube count if known.

Match

Review ranked results with match reasons and confidence scores.
Open a candidate to confirm on the full part page.
Use Photo ID if you have a top-down photo but need the part number.

Pro Identification Tip

A 2×4 with 3 hollow tubes and center ribs is almost always brick #3001. The same tubes without full ribs is plate #3020. A smooth cavity with a groove is a modern tile.