It's often said that "you can't have enough clamps". Clamps are used mostly for hold workpieces together firmly and accurately while glue sets up, but often serve simply as a "third hand", for stabilizing plywood panels while a cut is made with a portable power saw.
Bar clamps -- essential in the home shop, if you have larger projects that require gluing, especially table tops, or pieces that require edge-to-edge gluing. Bar clamps come in several different styles: Among older styles are A through F in the image on the left. Those marked B, C, and D are the heftiest, especially B. A is a special-purpose clamp, while E and F -- if purchased new -- are assembled in your shop after the wooden structural parts are purchased
C-Clamps: Also essential in the home shop, C-clamps are designed to hold smaller, narrow workpieces, such as table legs, while glue sets.
Named after its physical shape, the C clamp consists of fixed flat jaw and one movable jaw. The movable jaw has a flat “anvil” that pivots on a ball-joint swivel, allowing the clamp to adjust to securely holding some surfaces that are parallel or are nearly parallel. A threaded screw -- with a sliding pin handle -- adjusts the opening of the clamp.
When you purchase C clamps, two dimensions are important: the opening of the jaws, which can varies from 1 up to about 18 inches, and the depth of the clamp, which varies. The depth -- referred to as the throat – extends from the center of the screw to the clamp's "C" part. So-called "deep-throated C clamps" have throats extending up to 16 inches. The "depth dimension" of the throat determines how distant from the edge the workpiece can be clamped.
Hand-Screw Clamps: In function, similar in many respects to C-clamps, although achieving the same degree of pressure is not possible. The distinct of handscrew clamps is an ability to adjust to unique angles.