When I first installed the standingseam steel roof on my shed, I handbent the hems with a $12 sheet metal folding tool. It got the job done but it took forever, the results weren't great, and my wrists hurt for a week after the project. Needless to say, I wasn't a big fan of the process.
For shorter bends the cheapo bender was just fine, but my starting and ending panels each had a fulllength hem, and working in that bend for the full 14 feet of four panels just killed.
So I looked around and found a really cool looking tool to make the job easier. It had a series of opposed rollers that could be run along the edge of a piece of sheetmetal back and forth as pressure was applied to fold it up. It would gradually crease the panel and work the edge up further and further until the desired angle was reached. It could be adjusted for different sizes, and had multiple stations so it could be run right to the edge of the panel without losing it's reference. I watched a few videos and it looked like the perfect tool for my job.
The only problem was that it was crazy expensive! There are several flavors of these things made by various manufacturers, but the Malco (on which I based my build) was something like $600! This was a little while ago, and it seems prices have come down a bit since then, but I still see them listed online for between $539 and $822. Also, it looks like you can now get knockoffs for a little over $300.
But even at the low end, that seemed like way too much money for a tool I was going to only need twice.
It looked simple enough, though, so I resolved to make my own. I spent about $22 on 8mm precision shaft material, a pack of 602 2RS skate bearings, and some shaft collars, then cobbled the rest together from wood, screws, and bolts I had on hand.
It won't hold up like the $600 version, but for me it should work just fine.