Abstract: A leaf spring integrally formed of resilient sheet material has a transverse, substantially tubular arcuate intermediate portion terminating in opposed, laterally outwardly-extending, substantially flat abutment leaf portions. The tubular portion of the spring is adapted to be circumjacently received about the pintle rod of the usual hinge mechanism hingingly interconnecting the seat with the cover of an ordinary toilet seat assembly, with one leaf member abutting a rear portion at the inside of the seat and the other leaf member abutting a rear portion at the inside of the cover, to resiliently constrain the seat in down position against the reactive force of the cover when in its uppermost or open position, so that the seat can only be withdrawn from bowl position by manual lifting against the reactive force of the spring.