These feather-weight (less than .8g), thin (.055″), super strong cleats are the heart of this new system. Combined with installation cauls and strong magnets, they allow you to glue both the crack and the cleat in one operation. Once everything is located and aligned, the cleat can be installed perfectly in less than 60 seconds, finally making hide glue a viable option. The grain is oriented at an angle (22.5 degrees, matching that of prewar tone bars), which is about the only thing they have in common with their earlier predecessors, the diamond and disks cleats.
If you ever need to uninstall the cleat, it can quickly be removed (if glued with hide glue, other glues will take longer) by laying a warm damp sponge on top of it. In a few minutes, you’ll be able to lift the cleat out. Any residual hide glue can be removed with warm water and a small sponge.
Mahogany, maple and Adirondack spruce cleats are 6″ long. Rosewood cleats (CITES-safe Honduran or amazon) are at least 4″ long (the longest span you’re likely to encounter between back braces).
If you order multiples of rosewood cleats, you can expect to receive a variety of different colors and grain configurations.
Since the invention of the acoustic guitar, we (flattop/back repair peeps) haven’t had a crack repair method that was designed for and suited to our needs. Thanks to the advent and availability of neodymium (extra strong type of rare earth) magnets, now we do. Previously we had adapted and adopted the diamond and disk cleat method commonly used and ideal on carved orchestral instruments. Unfortunately, it is not ideally suited to our needs. We can’t just pop a top or back off and on! We make every effort to install cleats straight and on the crack, but even if we succeed, we are only reinforcing one small section of the crack at a time. As each short section of cleat dries in place, we often see shrinkage in the reflection in top where each cleat is located.
This crack repair system will level the surface along the entire length of the crack, in many cases making it completely disappear — a lifesaver if you happen to have a center seam open up on a new build in progress.
I recommend using hide glue, which is mostly water. The water will help to swell the two sides of the crack back together, making it much less visible.
I keep a few of the spruce cleats taped in the window (facing the sun) for vintage guitar repairs. They quickly darken in color to match the old spruce.