There is a small thumbturn screw on the bottom of the jackknife that is used to hold the pick in place (stop it collapsing back into the handle) once it has been extended for use. Parapilot is suggesting that this is easily lost making the tool, well, useless (or should that be more useless

)
You are really better off spending your money on something else. If you don't want to buy the 15pc get the 9pc, if that's too expensive try to buy individual picks (a couple of hooks and a half diamond for starters) or try making your own