locking noun. 
['lɒkɪŋ] E17.[from LOCK verb1 + -ING1.]1.  The action of 
LOCK verb1; an instance of this. Also with adverbs. 
E17.locking plate, 
locking ring, etc.
■ P. O'Donnell I'll see to the locking-up. Motor Boat & Yachting The steel hull will take all the knocks and bumps of continual locking. ■ B. Moore Heavy doors clanged shut and he heard a locking sound. attrib.:
2.  A mechanism for locking something. 
M17.  [TahlilGaran] English Dictionary ▲