Those are seriously impresive party tricks there, Yknarfy.
Nerchia, I think what you're referring to is called phimosis. This is when the natural opening in the foreskin it too small to allow it to retract behind the head during erection.
It can be extrodinarily painful for the man not just during sex but even just getting an erection in some cases. My ex fiance had this problem. because the foreskin was so tight the head of his penis couldn't become fully engorged so his penis tapered from a thick base to nearly a point at the head. Sex had to be done with the utmost of care.
Milder forms of this condition can sometimes be solved with gradual stretching of the foreskin. In more severe cases, as his was, partial or complete circumcision may be the only options. He chose to have dorsal slit created by surgery, basically just one cut vertically down his foreskin so that it opened a bit like a tulip. I thought that this would look ridiculous but once it healed it worked like a charm. The foreskin didn't flap back like a page, as I had expected, but rolled back as it was intended to.
And, oh, wow, what a difference it made. Once the full shaft and the head were able to become fully engorged...did I say "Oh, wow!".
Get this, though. He refused general anesthesia and watched the procedure being done. Farm boys are crazy!