A stapler apparatus includes right and left side frames each opposing the other, a reciprocally moving staple driving member arranged between the side frames, a cam member interlocked to the staple driving member to reciprocally move the staple driving member and a drive motor interlocked to the cam member. The drive motor, the cam member and the staple driving member are arranged in order between the left and right frames.
A counterforce-counteracting device for a nailer comprises an active device, a rotating member, and a weight device. The active device drives the rotating member and the weight device to move. After the active device moves, the weight device is driven by the rotating member to produce a counterforce, so as to counteract the counterforce of the nailer. Thereby, such a device is secure and is easy to assemble.