Why should the screws be divided into cross and groove? Why should the screwdriver be divided into one prefix and crosshead?
Because the screw on top of different lines, there is a bar, with a screwdriver, on top of a cross, cross with flowers, flowers cross screw is not easy to slip and, if a font is not very deep or thin blade screw you up, difficult and easy to slip, can't do anything.
Screw short, with a word, fastening force larger, longer screw, with cross, ten Zi than word, bear great force.
The word is the head of the screw, then rebuilt the crosshead (labor-saving and convenient machine or electric tool) screws, but the traditional one head screw people did not immediately give up, so there are two kinds of head screws on the market at present.
