the.com/doorstop
A wedge with one job, performing it with the ambition of a brick.
means A heavy or wedge-shaped object that holds a door open or keeps it from slamming into the wall.
from Plainly literal: a stop for a door, joining 14th-century stop (to plug or block) with the obvious noun, no metaphor required.
Book insultA massive dull book is called a doorstop.
Spring kindThe wall-mounted coil children love to twang.
Doorstep cousinOne letter apart, opposite purposes entirely.