Repairing stringed musical instruments when there is no manual (sometimes not even visual) access to the interior has always been a challenge. The techniques described and illustrated here will enable an accomplished luthier or repair person to reliably repair top cracks and install cross-cleat reinforcement without access to the interior except through the soundhole, with complete confidence in the integrity of the work.
The first step in the process is clamping and closing the crack itself. Pairs of super magnets have been used for some time now for these situations, enabling the edges of the crack to be accurately aligned with each other. What has been missing is a way to guarantee that the inner magnet will not be captured by stray glue inside the instrument, beyond reach and retrieval. The Bear Meadow contribution of this is a Teflon cap, machined to very thin walls (.020" thick), which is a slip fit on standard 9/16"x3/16" magnets. The use of this cap as a shield between the magnet guarantees that the magnet (nor the cap!) get glued in place, regardless of any glue used.