This is a removable lockout key for Kwikset keyways.  Please use it carefully and legally. Do not use it if you don't understand it. Use it only on locks you own.  I made the lower blade as thin as I thought wise.  It can still be hard to insert in narrower keyways, especially Smartkey locks.  Print it as smooth as possible top and bottom, make sure there are no zits on the print and lubricate the lock.  If you still have problems inserting the blade, try reducing the z axis height by a few percent.