- The barrel is in two parts so the knob can be turned to lie flat and secure the cranked section. A good idea but in practice both bolts that I had fitted by a very good joiner came apart in his hands as they had in mine and the tiny spring and ball bearing were lost. Now when I open the bolt the cranked section stays in the keep. I intend to solve this for the bottom bolt by super gluing the two sections together. For the top bolt hopefully gravity will come to my aid so I can retain the security in folding the knob flat.