I'm planning to make a couple of houses for owls and bats around my property to help control vermin. I've been looking on youtube.com at the owl houses and being one of those people who tend to go a little overboard with detail, I see all kinds of things I don't like. I saw one woman build an owl box where she designed the top with vents that would literally direct rainfall down into the box. I also saw lots of other things I didn't like, such as screws in the roof that will allow an entry point for water and many other things.
I'd like to put vents up the side, but I don't want rain running in. To accomplish this, I'd like to make them angle up into the box at a roughly 30-45 degree angle. I'd like to know the best way to do this. My first thought is to take a circular saw and set the angle on its blade. I'm not sure if mine is capable of that or not. I also have access to a table saw. It seems like it'd be simple to set the angle and cut a line, but how do you get the blade into the board? You can easily make and interior cut with a table saw or circular saw by setting it down into the board, but at an angle, it doesn't seem like it'd work the same. Can anyone tell me how to do this?
Again, these are just vent holes, probably about 5-6" long in a 1"x10-12" board. I don't want to make straight cuts and then add an angled vent on the outside as it won't last and will be a week spot. I'm basically wanting to add a few angled slots and inch or two apart. Thanks for the help.
Edit: Here is a mock up of what I'm trying to do. Let me know if it's not clear and I'll try to do better.