Keyed different (KD) padlocks use separate operating keys; keyed alike (KA) padlocks share an operating key within a defined group. A master-keyed system adds a controlled key that can open a specified set of locks. The right choice depends on who must control each lock, how many locks each person needs, and how additional keys are managed.
For an industrial buyer, “144 safety padlocks” is an incomplete specification. A supplier also needs to know whether those locks form 144 different key combinations, 36 separate four-lock sets, or another approved arrangement. Getting this decision right before ordering makes issuing, replacing and expanding the lock inventory easier.
Compare KD, KA and master-keyed systems
| Keying arrangement | Which locks does an operating key open? | Procurement use to consider | Main control question |
|---|---|---|---|
| Keyed different — KD | Its assigned lock within the specified non-duplicate key range | Separately assigned personal locks | How are key codes and duplicates tracked? |
| Keyed alike — KA | Every lock in its designated KA group | Several locks assigned to one person under the site procedure | Who controls the shared key, and are other groups separately keyed? |
| Keyed different with master key — KDMK | Each operating key opens its assigned lock; the master opens the defined group | A specified hierarchy with restricted master-key custody | Who can access the master, and under what removal procedure? |
| Keyed alike groups with master key — KAMK | Each group shares an operating key; the master opens specified groups | Multiple separately controlled KA sets with an approved hierarchy | Is each group boundary clear in the order and site register? |
These are keying descriptions, not instructions to remove another employee’s lock. Naming conventions can vary between suppliers, so request a written key-opening matrix with the quotation.
When is keyed different useful?
KD gives each assigned lock a distinct operating key within the agreed key range. This can make it straightforward to issue one lock to one employee and record the lock ID against that employee in a register.
Ask the manufacturer to explain the scope of “different.” Does the non-duplicate range cover this purchase order only, existing locks at the same site, or future additions as well? A key combination selected without reference to previous orders can undermine an otherwise clear inventory system.
Also separate the keying arrangement from the number of keys supplied. KD does not, by itself, specify one physical key. If two copies are supplied, both copies open the same assigned lock. The site needs a custody rule for the additional copy.
When can a keyed alike set help?
A KA set can reduce the number of keys carried by a person who applies several locks during an approved task. The important detail is the boundary of the set. Four locks for one person should not be confused with four locks shared across four people.
Illustrative procurement example: a site plans to issue four locks to each of 36 employees. One possible specification is 144 locks arranged as 36 separately keyed KA sets of four, subject to the site’s approved personal-control rules. Each set needs its own group identifier. Ordering “144 KA locks” without that instruction could be understood as one shared-key group.
This example defines an order structure; it is not a substitute for an equipment-specific energy-control procedure. If several people work on one machine, key convenience must not replace each person’s required control.
What changes when a master key is included?
A master key creates an additional opening permission. It should therefore be a deliberate part of the specification, with named custody, restricted storage, a key register and a defined scope.
Under the U.S. general-industry rule, the person who applied a lock normally removes it. Employer-directed removal when that person is unavailable requires a documented exception procedure, including absence verification, reasonable contact efforts and informing the employee before work resumes. Possessing a master key does not replace those conditions. See OSHA 29 CFR 1910.147(e)(3).
Do not automatically include master keys because they appear to be a useful extra. Ask whether the site actually needs the hierarchy and whether its procedure addresses that additional access.
Key numbers, lock IDs and colors serve different purposes
A lock ID identifies a physical lock. A group ID identifies a set of locks sharing an opening permission. A key code identifies the key arrangement. Body color can support visual identification, but it does not tell you which locks a key opens.
Keep these fields separate in your inventory. For example, employee E036 may receive locks L0141–L0144 in KA group G036. That reference makes a replacement request more precise than “another red padlock.” The identifiers here are examples, not existing PROLOCKEY key codes.
Specify the system before requesting a quote
Send the supplier the following information:
- Total lock quantity and the number of employees or separately controlled sets.
- Locks per set and the required opening relationship between sets.
- Existing key-system references that the new order must match or avoid.
- Number of physical operating keys per lock or set, with spare-key custody requirements.
- Whether a master-key hierarchy is required, its scope and the number of master keys.
- Lock IDs, group IDs, engraving fields and expected future additions.
Review a sample set against the written matrix before releasing the bulk order. Confirm that intended keys open the intended locks and that keys from separate groups do not open them.
Frequently asked questions
Does KD mean exactly one key is supplied?
No. KD describes the opening relationship between locks. The number of physical key copies is a separate order field.
Can locks with the same body color have different keys?
Yes. Color and keying are separate configurations. Use a key register or group identifier rather than color alone to establish access.
Can a new order extend an existing KA group?
Potentially, subject to the manufacturer’s key-system compatibility and records. Provide the existing group reference and obtain written confirmation before ordering.
Plan your PROLOCKEY padlock configuration
Explore the PROLOCKEY safety padlock range or send your lock quantity and key-opening matrix through our custom safety padlock service. For dimensions and material selection, read How to Choose Safety Padlock Shackle Material and Length. For numbering and artwork, use the custom padlock order checklist.
Source and scope: keying terminology is explained using PROLOCKEY’s product and key-system materials. The cited OSHA provision concerns U.S. general industry; determine the rules applicable to your location and activity.