Cracks are the most common damage on Shakuhachi and other bamboo flutes mainly due to drying out. Here is a picture of my humid box.You can use any airtight container. If your flute has a crack, the best thing to do is place it in a humid environment - above 60% humidity. I put a few wet rags in the box to create the humidity. The crack will close in a day or two. Be sure to monitor the humidity level (not above 70%) and the duration. Mold may form if the flute is left in for more than 4 days if the humidity levels are too high. After the crack is closed, you can bind over the crack with a strong, heavy beading cord.I like Tuff Cord #6 or #7. 25 lbs mono filament fishing line is easier to obtain. See my topical bindings repairs.