Don't know how many types are out there,but ,
On the lock one I have=the barrel has small groves on the one end too lock it in place,to unlock and adjust you move it off the groves. The is a right and wrong way to use any adjustibles,the moving side of jaws should always be behind the force so load in at the bottom of moving jaw nearist the barrel vs at the top were there is more play in adjusted size.
