I generally crouched-down on the ground, to change rolls in my Nikon F, using my lap as a bench top. Less frequently, I managed while standing -- stuffing the removable back into whatever bag I was toting that day -- however, I found it too fiddly. Of course, the F2 effectively ended all this three-handed maneuvering. However, I was always concerned that someone might come along and walk into me -- a common New York City occurrence -- causing the F2 backdoor to be torn off. As a result, I mostly continued to rely on my F-style, lap dance. Oh! And one time some street photographer with a rather ancient Leica -- no doubt having perfected his own film changing technique -- approached me, only to turn away with scorn when realizing "the baby" in my lap was Japanese.