Clamps
Quick-release clamps with ten centimetres of opening, F-style woodworking clamps with a ratchet, a steel C-clamp, locking pliers, and lifting tongs for boards and stone blocks. The opening says how thick a workpiece fits between the jaws, the throat depth says how far in from the edge the clamp reaches. The jaws of a quick-release clamp can be turned around, and the tool then pushes apart instead of together. Lifting tongs close under the weight of the load but hold by friction, so on a wet or oily surface they drop it.
Clamps
A clamp holds the workpiece instead of your second hand, until the glue sets or the cut is done. The category holds quick-release clamps with ten centimetres of opening and twenty-nine kilograms of clamping force, F-style woodworking clamps with a ratchet worked one-handed, a steel C-clamp, locking pliers for welding, and a telescopic clamp for drawer fronts. The bodies are usually nylon with a hardened steel bar, the jaws swivel and are faced with PVC so they do not press marks into the wood. Lifting tongs for boards and stone blocks rated from three hundred and twenty-five to five hundred kilograms belong here too, along with a suction-cup solder wire holder for circuit boards.
Opening and throat depth are two different numbers, and these are the two that get confused most. The opening says how thick a workpiece fits between the jaws, the throat depth says how far in from the edge the clamp reaches. Gluing two battens together only needs a wide opening, while pressing edging towards the middle of a broad panel is decided by the depth. A C-clamp has little depth, F-clamps and bar clamps considerably more.
On a quick-release clamp the jaws can be turned around, and the tool then pushes apart instead of together. That helps with straightening a frame that has sagged, pushing apart a joint that has to come off, or holding a door open. It is the same clamp, only reversed, so a spreader is not something you pay for separately. On ratchet models you still control the pressure with one hand and hold the workpiece with the other.
The advice that a glued joint is ruined by clamping it too tight is stubborn, but with hand clamps a starved joint is practically impossible to make. The recommended pressure on the joint is about four to seven bar in softwood and twelve to seventeen in hardwood, which a hand clamp is more likely to fall short of than to exceed. The practical rule is to spread a thin even coat and tighten until a continuous bead of glue squeezes out along the whole joint. Joints that come apart were usually glued too late or with too little glue, not clamped too hard.
Lifting tongs close under the weight of the load, so the heavier the board, the harder they grip it. They hold by friction, though, which is why on a wet, oily or dusty surface they drop the load, and the same happens once the arms open at too wide an angle. Nobody stands under a suspended block, and the load is never guided by hand.