PURPOSE: To make it possible to easily and reliably retain a wire member such as electric conductor even with a relatively fragile wall by gradually penetrating bendable tips of nail-like portions along guide holes of a protection cover as the main body of a staple is inserted to a wall thereby tilting the tips inwardly or outwardly for anchoring the staple.

CONSTITUTION: A staple 1 comprises a channel-shaped main body 2 and an attached protection cover 3. The main body 2 comprises nail-like portions 2a arranged almost in parallel to each other and a bridge portion 2b between the nail-like portions. Also, the protection cover 3 is channel-shaped with guide holes 4 made at its left and right ends for inserting the nail-like portions 2a. The nail-like portions 2a are guided by the guide holes 4. The interval of the guide holes 4 is almost equal to that of the bridge portion 2b at the top and can be slightly separated or closer from the top to the bottom. By doing this, each nail-like portion 2a can be slanted and inserted to the wall thereby creating anchorage in the wall for easily and certainly retaining an electric conductor even in a fragile wall.