Abstract: A portable power operated fastener driving device including a work contact assembly having a manual adjusting mechanism for adjusting the extent to which fasteners driven by the fastener driving element of the device are countersunk into the workpiece. The manual adjusting mechanism includes a manually operable member movable by manual engagement to effect an adjustment of the adjusting mechanism and a releasably lock movable between a locking position for locking the manually operable member against manual movement and a releasing position enabling the manually operable member to be manually moved. A guard assembly encloses at least a portion of the adjusting mechanism including the manually operable member. The guard assembly includes a manually operable access door movable between a closed position wherein the manually operable member is manually inaccessible within the guard assembly and an open position wherein the manually operable member is manually accessible.