Image Item No. Description By  bslot01  Brick 1 x 2 without Bottom Tube, Slotted (with 1 slot) Catalog: Parts: Classic 3  bslot02  Brick 2 x 2 without Bottom Tubes, Slotted (with 1 slot) Catalog: Parts: Classic 1  bslot04a  Brick 2 x 4 without Bottom Tubes, Slotted (with 2 slots, opposite) Catalog: Parts: Classic 7  bslot17  Brick 4 x 4 Corner without Bottom Tubes, Slotted (with 2 slots) Catalog: Parts: Classic 1  bdoor01  Door for Slotted Bricks Catalog: Parts: Classic 1