Bellying (or the bowing outwards of the guitar top and bottom) is caused over time by the upwards and forwards pull of the guitar strings. Amongst other problems, bellying causes the bridge to rise thereby raising the action to the point where the guitar becomes unplayable.

The Bridge Doctor is a removable device that installs easily through the sound-hole. A mounting block is fitting under the bridge via a screw. A tension rod is then installed between the mounting block and the tail-block of the guitar. A grub screw in the mounting block is then tightened against the tension rod. This added tension on the bridge from the JLD Bridge Doctor counteracts the pull of the strings and the warpage of the top.