That circular saw looks good to me, but it might be difficult to cut the crotch of branches. For the bevel cut, they mean the blade can be turned sideways. It doesn't need a mount. Anne has featured some cat trees made by someone, I don't remember his name, but he would be a better person to ask.A while back I called a local Woodcraft store and asked for advice on this, and I was told that what I probably needed was a hand held jigsaw. They recommended that I check out garage sales and estate sales. They also very specifically recommended either a DeWalt or Sears jigsaw, but when I start getting that picky the chance of finding it becomes vanishingly small.
The thing is, the cat condo plans I have recommend using branches. I've been saving branches specifically for this, and with a jigsaw it becomes easier to select the right angle for cutting. At least, I think that's the issue.
They do also have this: http://www.harborfreight.com/7-14-in-10-amp-circular-saw-69079.html. The thing that bothers me about this saw is
That sounds to me like it requires some sort of mount, in addition to the saw, that it's not hand-held. And I don't know how much the mount would cost.
Margret