Is there a standard for reference characters in a figure with multiple instances of some object?

For example, if I have a drawing with multiple identical client devices, should they all have a unique label, or can I use a scheme like 302a, 302b, ..., 302n?

In the latter case, can I refer to them all collectively as 302 in the description?

If they all must have a unique number, like 302, 304, 306, should I refer to them in the description as "client devices 302, 304, 306" or "client devices 302, 304, and 306" every time?

I do not see this addressed in 37 CFR § 1.84.

Most relevant section:

(p) Numbers, letters, and reference characters.


(4) The same part of an invention appearing in more than one view of the drawing must always be designated by the same reference character, and the same reference character must never be used to designate different parts.

  • I'm pretty sure you use the same number for all references, but I'm not a lawyer so I'd like to wait for an authoritative answer.
    – Eric S
    Commented Dec 5, 2022 at 23:02
  • 1
    One thing you mention that should not be done - have a 301a, 301b, etc. and refer to them in the spec collectively as 301.
    – George White
    Commented Dec 6, 2022 at 17:32

1 Answer 1


I do not think there is a general standard.

What I often see is that if the devices are identical and it does not matter which is which, the said devices get the same numbers. For example, if the patent is about an AVR with better filtering the sound. In this case, the filtered sound signals is played by the loudspeakers 302.

And if the devices sligthly differ, or for the sake of the application it is important to identify them, it seems better to use 302a...n. For example, if the AVR is giving a spatially better experience, you may write that the corrected signals 301a-e are played by the corresponding loudspeaker 302a-e.

Some of my colleges keeps the same numbering across the application, and some are giving a new number for the same device on every figure.

Important is that you follow the regulations related to drawings. In case of a European patent it is Rule 46, especially Rule 46(d),(g),(i).

Rule 46(d):

All numbers, letters, and reference signs appearing on the drawings shall be simple and clear. Brackets, circles or inverted commas shall not be used in association with numbers and letters.

Rule 46(g):

The height of the numbers and letters shall not be less than 0.32 cm. For the lettering of drawings, the Latin and, where customary, the Greek alphabets shall be used.

Rule 46(i): 

Reference signs not mentioned in the description and claims shall not appear in the drawings, and vice versa. Reference signs to features shall be consistent throughout the application.

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