US Patent 7562857 Attaching structure

A design part composing a lamp unit includes a plate part positioned at a cabin side and covering an attaching hole of a roof trim, and a pair of vertically extending parts. The vertically extending part includes a frame part vertically extending from the plate part in a direction perpendicular to the plate part, and a movable piece continued to a connecting part of the frame part at a far side from the plate part. When a function part is pushed into between the pair of movable pieces, the gap between the movable pieces is increased, and a locking margin between the movable piece and an outer edge of an attaching hole is increased. Thus, holding force to hold the roof trim is secured.