A screw comprising: a shank including an insertion tip and a head end spaced from the insertion tip along a longitudinal axis, with the shank further including a straight portion between the insertion tip and the head end, with the head end being greater than the straight portion in an outer diameter and including an upper portion and a lower portion which is adjacent to and tapered toward the straight portion, with the upper portion provided with a pointed cutting portion circumferentially designed at a bottom thereof; and a first thread spirally disposed on the straight portion of the shank and including a plurality of asymmetrical thread convolutions, with each of the asymmetrical thread convolutions having a first cutting face facing onto the insertion tip and a second cutting face backing onto the insertion tip, with an included angle between the first cutting face and a horizontal axis perpendicular to the longitudinal axis being between 25 and 45 degrees, with an included angle between the second cutting face and the horizontal axis being between 3 and 23 degrees; characterized in that a plurality of anti-screw-out teeth protrude from a circumferential surface of the lower portion and each anti-screw-out tooth includes a guide face and a stop face, wherein the guide face of each anti-screw-out tooth extends outward from the circumferential surface in a tangential manner such that an included angle between the guide face and the circumferential surface of the lower portion is between 90 and 180 degrees, with a recessed channel formed between the stop face and the circumferential surface of the lower portion. a shank including an insertion tip and a head end spaced from the insertion tip along a longitudinal axis, with the shank further including a straight portion between the insertion tip and the head end, with the head end being greater than the straight portion in an outer diameter and including an upper portion and a lower portion which is adjacent to and tapered toward the straight portion, with the upper portion provided with a pointed cutting portion circumferentially designed at a bottom thereof; and a first thread spirally disposed on the straight portion of the shank and including a plurality of asymmetrical thread convolutions, with each of the asymmetrical thread convolutions having a first cutting face facing onto the insertion tip and a second cutting face backing onto the insertion tip, with an included angle between the first cutting face and a horizontal axis perpendicular to the longitudinal axis being between 25 and 45 degrees, with an included angle between the second cutting face and the horizontal axis being between 3 and 23 degrees; characterized in that a plurality of anti-screw-out teeth protrude from a circumferential surface of the lower portion and each anti-screw-out tooth includes a guide face and a stop face, wherein the guide face of each anti-screw-out tooth extends outward from the circumferential surface in a tangential manner such that an included angle between the guide face and the circumferential surface of the lower portion is between 90 and 180 degrees, with a recessed channel formed between the stop face and the circumferential surface of the lower portion.