PURPOSE: To ensure proper engagement of a plug to be fixed by means of a hot melt adhesive into a punched opening of a plate by making the snap- fastener blade of the plug so flexible that it can absorb dimensional error of conventional degree of the opening.

CONSTITUTION: A plug 1 comprising a molded plastic material body 2 with a flange 4 and a bead 3 of a hot melt adhesive deposited onto a peripheral surface of the body below the flange and around a surface 5 transverse to the peripheral surface. The plug 1 has at least one snap-fastener blade 8A having an insertion ramp and a retaining lip 14. For example, when an oval wall 6 is pushed into an oval opening, the snap-fastener blade 8A bends toward inside, then resiles such that the retaining lip 14 engages with the inside wall of the opening from underneath. The distance between the attachment end 10 and the free end 11 is greater than the distance between the peripheral surface of the flange 4 and the foot 13 of the insertion ramp, and the blade 8A is defined by an L-shaped groove 9 thus increasing flexibility.