Some doors have locks with knobs formed by a pin is driven. Interior door knobs tenement neck a small screw that secures the end of a square shaft. If the knob is apparent, probably the screw is loose or been lost; tighten or install a new one. Perhaps, it is necessary to do the same with the interior door knobs on the other side to maintain proper tension. There are some knobs attached to the axle with a screw and nut; ensure these are located in good condition. In other interior door knobs are screwed onto the shaft. If the thread is worn, wrap a small piece of plastic tape. If it does not solve the problem replace shaft.
Pick the lock knob that suits you and install it following the manufacturer’s instructions; Door openings are made in the same way as for installing a lock asleep. When the safety is depressed, the slot to open the door by inserting any key and turning. For interior door knobs you can use simple locks, no insurance and no slot. If it is a door to the outside, use a lock that opens with a key in one of the knobs and are insured in the other.