Originally Posted by ntnBO
While the Old Course doesn't discriminate against gender, they do discriminate against lack of skill. There is a handicap requirement in order to play and it must be displayed when you check in at the starter's hut. None of the other courses at St. Andrews have that requirement however.
FWIW I never had to show proof. They did ask when they went through the line of singles in the morning and told us we'd have to show proof at the starter's hut when we paid, but when I got to the starter he didn't ask for it. But I've heard stories of having to show proof, so to be on the safe side I'd take something with you (and fake it if necessary).
Also, to go along with what Bo said earlier, even if you can't get anyone to go with you to St. Andrews, go anyway. Plenty of b&b's have single rooms, all you have to do to get on the Old Course is show up early (okay, very early) in the morning, and all the other courses I was able to walk on pretty much whenever I wanted. I can't comment about any of the courses outside of St. Andrews, but if you can do a trip, then go, regardless of whether anyone wants to come along.