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Rule out the usual hiding places first. If the piece really is gone, check the set piece by piece and leave with the element ID LEGO asks for, or a link to buy the part.
Builders who report a missing piece often find it in one of these places. Tick each one off as you look.
These parts appear in this set in two colors that are easy to confuse. If you are one short in one color, check whether it went in where the other color belongs. Each color has its own element ID in the parts list at the back of the instructions.
Brick 2 x 3 without Cross Supports
White ×4
Trans-Clear ×2
Trans-Clear is see-through: hold the piece up to a light.
LEGO's request form asks for the set number (312-4) and each piece's element ID, both listed above.
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Brick 1 x 1
×4
Brick 1 x 2 without Bottom Tube
×8
Brick 1 x 8 without Bottom Tubes with Cross Side Supports
×6
Brick 2 x 2 without Inside Ridges
×2
Brick 2 x 4 without Cross Supports
×17
Brick 2 x 8
×6
Brick Round 1 x 1 Solid Stud, No Bottom Groove
×4
Brick Round Corner 2 x 2 Macaroni with Stud Notch
×6
Brick 1 x 1
×6
Brick 1 x 1 with Blue '1' Print
×2
Brick 1 x 1 with Blue U Print
×2
Brick 1 x 2 without Bottom Tube
×6
Brick 1 x 8 without Bottom Tubes with Cross Side Supports
×4
Brick 2 x 3 without Cross Supports
Also in Trans-Clear
×4
Brick Round 1 x 1 Solid Stud, No Bottom Groove
×2
Plate 6 x 8
×1
Brick 2 x 3 without Cross Supports
×9
Window 1 x 2 x 1, Extended Lip, Hollow Stud [with Glass]
×6
Brick Round 1 x 1 Solid Stud, No Bottom Groove
×10
Brick 2 x 3 without Cross Supports
Also in White
×2
Tick each piece as you find it, or mark it missing.
LEGO takes requests for pieces missing from a new set through its customer service site. The form asks for the set number and each piece's element ID, the number printed beside the piece in the parts list at the back of the instructions. This checker lists both.
Request a replacement from LEGOMark a piece missing and your list links it to an eBay search for that part, which also covers pieces from older or second-hand sets.
Copy or download your missing list (the CSV opens in any spreadsheet), or print the whole checklist and tick pieces off on paper. Your marks stay in this browser, so you can check a big set over several sittings.
