Clamps close the joint; cauls keep it flat
Clamps pull along the length of the joint. They do nothing about the panel bowing across its width — in fact a row of clamps all on one face bends the panel towards them.
Cauls are stiff bars, slightly curved, clamped across the width above and below. The curve means they touch in the middle first and apply pressure outward as they are tightened.
Alternate above and below
Half the clamps under the panel, half over it. The bending forces cancel instead of adding.
Parallel jaws
A conventional F-clamp’s sliding jaw tilts under load and pushes the work out of plane. Parallel clamps hold ninety degrees to the bar, which removes a force you would otherwise be fighting.
Dry fit first
Everything above happens in the ten minutes before the glue grabs. Rehearse it.
What comes up most often
How many clamps for a tabletop?
One every 200 to 300 mm (7.87 to 11.8 in), alternating above and below the panel so the bending forces cancel. Six clamps make a small panel; twelve make a table.
Last reviewed 2026-08-12