I recognize the four common flake types of feather, hinge, overshot (or reverse hinge), and step that are found in most of the literature (Cotterell and Kamminga 1987:684; Patten 1999:85; Whittaker 1994:18). Plus, I add the full-length flake for a total of five. These types are defined by their crack trajectory and termination and not by their initiation. Each, with the exception of the hinge flake, can be created with either pressure or percussion (soft or hard hammer). Each can have the universe of bulbs of force. And, each can initiate under the force application tool or away from it (lipped flake). The factors that effect the creation of the various flakes are width-to-thickness ratio of the core, loading time of the force, and angle of blow.
Feather Flake -- a flake created by a single crack with a straight trajectory that exits the front face of the core. Therefore, it is a fractional flake or is shorter than a full-length flake. When these flakes are removed from a flat face, they are wedge-shaped as in the image. The flake scars of these flakes can have some heavy ripples at the end, but the trajectory of the crack is still straight. Full-Length Flake -- a flake created by a single crack with a straight trajectory that runs the full length of the core. As the crack approaches the far end of the core it will often turn, either toward front or back face, but it still exits the bottom of the core. Hinge Flake -- a flake created by a single crack with a straight trajectory until it suddenly, but gently turns towards the front face and terminates the flake. It is a fractional flake or is shorter than a full-length flake. Often as the crack approaches the front face, but long after it has turned toward the front face, it will again turn either up of down. If it turns up it creates the classic lip (reflexed termination) that is associated with hinge flakes. If it turns down, then the flake scar (inflexed termination) is often assumed to be that of a feather flake with a jump in the scar surface. The hinge flake is the only flake that can not be created with pressure. Overshot Flake -- or reverse hinge flake is created by a single crack with a straight trajectory until it suddenly, but gently turns towards the back face and terminates the flake. It has a trajectory that is the reverse of the hinge flake and hence, the second name "reverse hinge flake". It is a fractional flake or is shorter than a full-length flake. Step Flake -- a flake created by two cracks. The first crack is a straight trajectory that actually stops in the core because it consumes all the energy. When the first crack stops, a second crack caused by the knapper's follow-through breaks the flake off. It is a fractional flake or is shorter than a full-length flake. As in the drawing, evidence of the first crack extending beyond the end of the flake scar is almost always present because the second crack rarely begins at the very end of the first crack.