Spring Clamps

A spring clamp squeezes its jaws shut with a coiled spring, the same basic mechanism as an oversized clothespin -- squeeze the handles to open it, release to let the spring do the clamping. It's the fastest clamp in the shop to apply and remove, entirely one-handed, but the clamping force is genuinely limited by how strong a spring a person can comfortably squeeze open.

That makes a spring clamp right for light glue-ups, holding a featherboard or jig in position temporarily, or corralling small parts during finishing -- not for a structural glue-up that actually needs real pressure, where a quick clamp or bar clamp does the job a spring clamp can't.