A replacement for cylindrical dowel nuts is provided and is a hollow cylindrical nut with a threaded hole on top and an unthreaded hole at the bottom which is for the threaded shank to enter. This hollow dowel nut elastically compresses during tightening to act like a lock-washer to prevent loosening. Several solutions are provided to make the top of the nut thicker to fit more thread coils than what wall thickness would otherwise permit. To improve loosening prevention further and also provide overtightening prevention a hollow nut with flatter bottom and a narrow gap bisecting the lower hole are used which during tightening cause right and left edges of said gap to be pushed towards the bolt strongly gripping it which prevents overtightening and loosening. “C” shaped nuts also provided which cause misalignment and jamming in the thread when compressed thereby also preventing loosening and overtightening.