A protective sheath made of plastic, particularly for blades of hedge trimmers, includes a container (1) that has an essentially tubular side wall (2), which has a longitudinal axis (a) and a closed end wall (3) and is obtained by a method for injection-molding plastic material in a pasty state in the interspace of a mold that is composed of a male part that can be inserted coaxially in a cavity of a female part. At the closed end (3), the container has a hole (11) that is formed by a centering pin (104) located at the free end of the male part with respect to the female part during molding to ensure constancy of the thickness of the container. The hole (11) is removably closed, in a liquid-tight manner, by a removable plug (12) that is made of a elastomer material that is relatively more flexible than the basic material of the container. The method ensures a constant thickness of the sheath and is extremely cheap. <IMAGE>
