The sine bar and gauge blocks are the most accurate way to get an angle or test one that is already made.
Your imagination is the only limit to what you can do with one.
I have looked till I am blue in the face for my handbooks with all of the information already in tables and cant find it.
Here is a sine bar.
The trick to this thing is the distance between the centers of the two bars in the bottom.
To set the bar up you multiply the sine by the distance between the centers.
So if it is a 5 inch sine bar and you wanted to know how high to set it for 45 degrees you would multiply 5 X 0.70711=5.5355 which would be the height of the gauge blocks to set under one end.
I have calculators with these settings some place to but cant find them.
They are also on line.
How can this help you at home?
Lets say you wanted to cut a tree down and wanted to make sure you didn't drop in on the house.
You can use these same functions or stuff like it for finding out how tall the tree is.
This is how I found out the neighbor was about to drop a tree on his house.
He said it (((looks)))) like it wont hit it.
I told him the math doesn't lie the thing is going to take your back porch and truck out.
You can do the same thing with a compass to tell how far it is across a river or canyon.
You can use the thing to set up all sorts of stuff and make very accurate angle blocks for your saw or drill press.
Worth