A slap hammer including an adjustable striking member and a releasable retaining mechanism for releasably retaining a sliding weight is disclosed. One described slap hammer comprises a guide rod having a first end and a second end; a striking member coupled to the second end of the guide rod and movable relative to the first end of the guide rod; a sliding weight slidable along the guide rod between the first end of the guide rod and the striking member; a biasing element positioned between the sliding weight and the first end of the guide rod, the biasing element biasing the sliding weight towards the second end of the guide rod; and a releasable retaining mechanism for releasably retaining the sliding weight against the action of the biasing element.