Abstract: The present invention discloses a screw, which comprises a shaft, a head and a thread. The shaft has an awl on one end thereof. The head is formed on the other end of the shaft and has an engagement groove. The thread is formed on the surface of the shaft and spirally extends from the awl to the head. The thread has two surfaces whose edges are connected with each other to form a cutting edge. The thread includes at least one receiving groove having a guiding face, a collecting face and a connecting face. The connecting face connects the guiding face and the collecting face to form a debris-receiving space. The debris-receiving surface penetrates the two surfaces of the thread. The connecting face has a crushing portion with a ragged surface. Thereby, the screw can provide higher locking strength.