[saxmsy]

Great work! Btw, could OP or anyone just explain a little bit how this works to determine the tenon leak or not please? I understand that by tightening that butterfly nut, the rubber band will expand and seal well with inside of the tenon tube. But how can this tell if it leaks or not? Thx!

 

[saxmsy]

The Musicmedic version is here: Neck Checker
You're supposed to put it inside the body below the tenon receiver and above any of the toneholes, so that it seals off the body and isolates the neck-to-body joint. Then you put on the neck, close off the octave key, and blow into or suck on the end of the neck.

Thanks! Now I got it.