Flattop
A "flattop" is a type of short haircut where the hair on the top of the head is usually standing upright and cut to form a flat-appearing deck. This deck may be level, or it may be upward or downward sloping. This type of haircut is usually performed with electric clippers, either freehand or using the clipper-over-comb method.
Styling
When a flattop is viewed from the front, varying degrees of squarish appearance are achieved by the design of the upper sides as they approach and round or angle on to the flat deck. Possibilities, somewhat limited by skull shape, the density of the hair and the diameter of the individual shafts of hair include: boxy upper sides with rounded corners; boxy upper sides with sharp corners; rounded upper sides with rounded corners; rounded upper sides with sharp corners. The hair on the sides and back of the head is usually tapered short, semi-short, or medium.
A flattop might be graduated in length on the top of the head from one and a half inches at the front hairline to about a quarter inch at the crown to a half inch as it starts curving down the back of the head, tapering to the skin near the middle of the ears. A variant form known by several names including flattop with fenders and flat top boogie has long sides known as fenders with or without a ducktail.