Master Lock Discus Padlock

Check the shackle clearance before you buy. The 40D gives you 5/8 inch of vertical shackle clearance, 3/4 inch between the shackle legs, on a 3/8 inch diameter hardened shackle. That is a short, tight opening by design, so it only works on hasps with a thin staple and a small eye. If your hasp has a thick staple or you need to pass through a chain link or a thicker cabinet latch, the discus shape will not reach.

Yes. The 40D is offered keyed alike as well as keyed different. Keyed alike is what property managers and facilities buyers want when one key has to open every storage unit, gate, or tenant cage on a site. Keyed different gives each lock its own unique key when the openings need to stay separate.

When you order keyed alike, you can specify the key code. Stock codes offered are 0340, 0313, 0370, 0501 and 0452, and there is a free-text field if you need a different number that matches padlocks already in your building. In that field you can also state whether a substitute keyed alike number is acceptable if your requested code is unavailable. Give the code stamped on your existing key or lock so the new units join the same system.

The discus body shrouds the shackle. On the Master Lock 40 Series, the round stainless body wraps almost the whole shackle so there is very little metal exposed for bolt cutters to bite. A conventional padlock leaves both shackle legs standing proud, which is faster to cut. The trade-off is clearance: you only get 5/8 inch of shackle opening, so a discus lock is for hasps and gate latches with small staples, not for chains or wide shackles. If you need to pass through a chain or a thick staple, buy a long shackle padlock instead.

The body is stainless steel and resists corrosion, and the shrouded round shape sheds water off the keyway better than a squared body, so the 40 Series is a common pick for outdoor gates, sheds, and exterior storage doors. The shackle is hardened steel for cut resistance. Master Lock rates this one for residential duty, so for high-abuse commercial or institutional openings look at a heavier commercial-grade padlock.

It uses a 4-pin cylinder, which raises the effort over a basic 3-pin wafer or warded lock but is below a 5 or 6 pin commercial cylinder. There is also a key retaining feature, so the key will not come out while the lock is open, which stops the common problem of someone hanging a padlock on a hasp unlocked. For a residential-duty lock on a shed, gate, or storage unit that combination is reasonable; for an opening where a determined attack is likely, step up to a commercial padlock with a higher pin count.

Double deadbolt locking. Both shackle legs lock into the body rather than just one, so a pry bar or twist attack has to defeat two engagement points instead of pivoting the shackle out of one. Combined with the shrouded stainless body on the Master Lock 40 Series, there is very little purchase for a tool.