Hmm. They could be trapped somewhere (for some reason the three of them together got kidnapped) and because of the way they're arranged(cages?) Clint can't see Matt, but can see Foggy (who can see both). Maybe Matt also has a gag in his mouth, so he would have to communicate with *Foggy* through sign language (which he knows for some reason) and Foggy (who doesn't) has to try and describe what he thinks Matt is signing to Hawkeye to decipher. Which he doesn't do very well. They have to work together to break out of wherever they are, so the situation is slightly taxing.

Bonus scenario:

Matt: "Hmmmhmhmh?" (Translation: "Foggy? Why have you stopped describing what I'm signing?")

Foggy: "Uh, Matt, you're not gonna want to hear this, but...lights just went out. Can't see a thing anymore, sorry."

Matt: *muffled, but surprisingly understandable swear words*