Originally posted by stretch:

It's definitely about putting the cursor on the point you want to attach something to. Pieces have several points they can snap to and it can be fiddly figuring out the point you want but it's easy enough after a while.Only consistently difficult snap is when trying to attach something below yourself. You really need to be lower than the point you want to attach something to. It's possible from above but so much easier from below which I guess is because you cannot get the cursor over the point you want to snap to because you cannot actually see it.

It's a nightmare if you want to fill in a small hole just below a wall or something, you need pixel perfect aim and even then it might not be enough.
Or if you're trying to put another half wall just below a wall (because supposedly the continuation of the wall is floating), you're going to have a lot of trouble placing it.