Used

A smarter person than me (not to set the bar too low) might make a fruitful career figuring out the fluid dynamics of a crowd of commuters on a packed 4 train during the morning rush hour. The combination of the impenetrability of solids with the psychology of personal space, multiplied by the square of all the caffeine per ounce of blood on the train, came together to give me about half the amount of space I might actually occupy in any other venue.

I was as close to the door as I thought I could be without actually being OUTside the train, so it came as some surprise when a slender, well shaped female hand, light brown and long fingered, came to rest upon my shoulder. The hand, attached to a person I could not see behind me, gripped tight for a moment, using me as sort of a lever to pull herself into the train, wedging herself into a gap I didn't know existed between my back and the doors as they slid closed.