No wonder Story Ennis was so cold his jaws were clacking. It was already established that Story Ennis doesn't even wear socks, yet he took his boots off to sleep on what was presumable a cold night.
I think TJ raises an interesting point that I don't think I've ever seen discussed anywhere, in relation to either the story or the film. While AP gives us no direct evidence for it, was Ennis already hard when Jack put his (Ennis's) hand on his own (Jack's) erection?
Um, if I may speak from personal experience, this is a completely logical assumption under the circumstances. ...
The Story Ennis did not even own underwear in 1963. And, while Jack might have an extra blanket, the book does not say.
Speaking from personal experience, too, and knowing how there is an "evidence of clear slick" which usually only appears when a man is sexually aroused or being made so, I believe that Ennis did already have an erection. And, unless there has been lots and lots and lots of foreplay for a man, a little more lubrication, like spit, is needed for better ease to enter.
IMO, the scene is too abrupt and knowing the personality of Ennis and how he would have reacted if Jack had suddenly forced Ennis to touch his penis, I just believe that Ennis Del Mar would have given Jack Twist an attitude adjustment first, by slugging him, and then ask questions later.
Anyone who would say "I'm not no queer" and literally believed that to be true about himself and be an Ennis type, too, would not have let another man even touch him if sex was going to be involved.