cool What is the reasoning for the two piece bottom, main body and second shaft, ? The one i have is built with the thumb piece has a tube attached that slips over the shaft on the main body. There is a pressed dimple or punch mark on the tube if you will that keeps the finger rest tube from coming off the shaft. There must be a groove the the dimple rides in hidden inside the tube. I can post you a pic if you would like, a set screw would/ could do the same thing. The construction methods used on my swivel knife are Knurled Main body with the blade held in with a set screw, A second threaded shaft which screws into the top of the main body for length adjustment with a jamb nut to keep it in place then the finger rest and tube that slips over the top of the second shaft that is held in place with a pressed dimple riding in a groove on the top of the adjustable shaft that allows for the pivoting action.