keyholes can be challenging at first, but its all about paying attention to detail. If you really study the problems that you got wrong and really pay attention to all the details of the shape, there is always one clear answer.You just have to keep practicing, as much as you can, and you should get the hang of it. The first time I took the DAT, the keyholes all seemed a lot harder than the practice tests I took. Then I re-took it again a few months later, after re-studying the same prep material that I had, and the keyholes seemed sooo much easier the second time. I guess I just had a better eye for it after more practice.
And don't worry if you get a few keyholes wrong. The other sections are a lot easier, and I think you can get like 5 wrong on the PAT and still get 99th percentile.