Screws

A screw, comprising:

• a shank;
• and
• a threaded section spirally formed on an outer surface of the shank, the threaded section including a plurality of joined threaded units each having a length greater than a pitch, each of the threaded units including a closed curve having two opposing first curved sections and two opposing second curved sections;
• wherein one first curved section is disposed between the two second curved sections and one second curved section is disposed between the two first curved sections;
• wherein each of the threaded units further comprises two opposing high points each formed between the first curved section and the adjacent second curved section and two opposing low points each formed between the first curved section and the adjacent second curved section;
• wherein one high point is disposed between the two low points and one low point is disposed between the two high points;
• wherein a width of the threaded unit at the high points is the greatest and a width of the threaded unit at the low points is the least;
• and
• wherein the width of the threaded unit is decreased from the high point to the low point.