How it holds. The panel is 6 mm of PETG with an 8 × 8 grid of 8 mm square holes on a 20 mm pitch, and four countersunk holes on the solid webs between them for #8 screws into wall anchors — every hole stays free for a peg. Each piece carries square split pegs: a 7.4 mm shaft with a slot down its middle, a barb on each half that rides in through the hole and springs out behind the panel; both faces of the barb are 45°, so the piece prints on its back with no supports and a straight pull releases it. Walls are 2.4 mm, hooks 6 mm, shelves carried on two gussets. PETG is tougher than PLA and shrugs off a warm garage. Add a panel later and it lines up with the ones you have.