To prevent an infant from being injured by a razer comprised of a convenient razer having a handle front segment acting as a blade installing segment and having the blade projected from below in a downward direction and a shield-shaped cap fitted to the blade installing segment by a method wherein the cap cannot be removed from the razer unless both right and left side plates of the cap are pushed inwardly of the cap and the cap is pulled manually while being pushed.

A shield-shaped cap is formed by a resilient material. Both right and left side plates 13, 13 are curved outward in a lateral direction to overhang at 19, 19. The curved overhangs 19, 19 are pushed inward of the cap and the cap can be pulled out only when they are resiliently deformed in a substantial vertical state.