Here are some of the uses I have for my spool clamps in my shop:
Snugging down stubborn wooden binding that I can't secure with masking tape or stretch tape.
Fit and glue the instrument back to the sides.
Helper clamp when gluing top or back plates to the sides of the instrument. This can be at the neck or butt block areas or in the waist area.
Repairing a crack that may have formed in the instrument side during construction.
Repairing a top or back plate that may have inadvertently lifted a bit or separated from the lining or block areas.
While you certainly do have other tools in your shop that you can use to make these repairs, for some tasks, the Spool Clamp is the most elegant tool to use. You have very precise control over clamping pressure with a very compact tool and other, more bulky tools can make a bad situation worse.