A padlock is composed of a body, shackle,and a locking mechanism. The typical shackle is a "U" shaped loop of metal (round or square in cross-section) that encompasses what is being secured by the padlock (i.e., chain link or hasp). Generally, most padlock shackles either swing away (typical of older padlocks) or slide out of the padlock body when in the unlocked position.
There are two basic types of padlock locking mechanisms: integrated & modular. Integrated locking mechanisms directly engage the padlock's shackle with the tumblers. Padlocks with integrated locking mechanisms are characterized by a design that does not allow disassembly of the padlock. The more modern modular locking mechanisms, however, do not directly employ the tumblers to lock the shackle. Instead, they have a plug within the "cylinder" that, with the correct key, turns and allows a mechanism, referred to as a "locking dog"to retract from notches cut into the shackle. Padlocks with modular locking mechanisms can often be taken apart to change the tumblers or to service the lock. Modular locking mechanism cylinders frequently employ pin, wafer, and disk tumblers.

ITEM	SIZE	Qty(Doz/Ctn)	Measurement	Weight
				G.M	N.M
HL816	16mm	100	46×26.5×25	36	30
HL820	20mm	50	51×32×17.5	27	21
HL825	25mm	50	59×34.5×18	48	42
HL830	30mm	40	55×41.5×19.5	53	57
HL840	40mm	20	51.5×32.5×22	47	41