One of the things I have found is that uniquely to the usual status quo of researching airsoft matter, when it is a question of what something is called, usually those with the specific, namely forces related knowledge, are much more likely to be able to provide an answer within 10 seconds than I can in 10 minutes, even if you have to wait for them to answer. I would guess equally to yourself, but that does not help me to find out what they are called, or how they operate. I think it is also possible they're not for that purpose.
My best guess was that they were attaching knee pads by bungee cord.