Flowers48/m1758
I agree with you that there is virtually no distinction between a foot rest and foot stool. Both are manufactured to anticipate the weight of the user. If the Postal Service is claiming that there is a distinction then the union should request some type of definition to show that distinction. The parties should also rely on the manufacturers flyer or safety instructions that came with the footrest/footstool that might define what the equipment is, or is not, supposed to be used for. Further, if there is a distinction, then I would put the onus on the Postal Service that it is their responsibility to train employees, usually through service talks, what that distinction is. If they haven't done that, then I would also argue that the Postal Service has a responsibility to adequately and visibly mark any equipment that may be inadvertently used for the wrong purpose. And what was it again that your union was doing for you?
As for whether or not these circumstances are sufficient to establish a prima facie case of discrimination - without having seen the wording or language of the discipline it would be difficult to say. Applying your weight to the footstool, regardless of your size, could merely be a description of how the event happened. The Postal Service may "regard you as" an individual with a disability, even if you would not otherwise meet the definition of "an individual with a disability" under the Rehabilitation Act, if you can show that their inference to your weight was an inference that your weight interfered in your ability to perform the essential functions of your position.
So I was rather surprised that some of those that responded to your post automatically assumed that the problem was with your weight. You didn't say that you actually had put too much weight on it - only that the P.O. accused you of putting too much weight on it - which they also claim was not what it was designed for. Initially I don't see this as an EEO complaint, I see it as the P.O. covering their hiney for not properly marking their equipment to ensure the safety of its workers, and the union failing again to......well you don't need me to tell you what you already know.