Abstract: In a hand-held circular power saw, a mechanism whereby a blocking pawl moves into the path of a projection fixed to the rotatable blade guard of the saw, preventing motion of the blade guard and protecting the operator. The blocking pawl is moved into the blocking position during the opening of the blade guard, when the projection fixed to the blade guard tangentially forces a cam-shaped surface to rotate, the cam-shaped surface thereby forcing the blocking pawl into the return path of the blade guard projection. The pawl is kept in this position by means of a spring biased arm which is forced against a toggle such that motion of the lever is prevented.