Device for protecting number plates

The device has a flat bottom (1) whose front surface comprises two longitudinal projecting edges (2, 2 ') provided with corresponding longitudinal grooves (3). The grooves extend on inner faces (4, 4 ') of the corresponding edges. The inner faces are arranged against each other such that the grooves are arranged in a same plane, where the device is made of a shape memory elastic material such as rubber, elastomer and elastomer derivatives. The bottom has a rear surface that is provided with hollowed longitudinal edges.