One of the first things you're gonna have to do when you get a hand plane, whether you buy one at the store, or a flea market, is flatten the sole. And, if we look at the bottom of the plane, this big, flat surface here is called the sole.
This is what you're indexing off of to make your cuts with the plane and if it's not perfectly flat, you're gonna have a very hard time getting a good quality cut. Now, most planes, when they come from factories or if they've been hanging around a garage for a while, may not have the flattest of soles and you're gonna have to do some work to get it that way. The easiest way to do that is to set up a little board. Now this board should be a piece of float glass or a piece of granite. So, you'll wanna put some emery paper or, you know, some wet/dry sand paper, put it with some spray-on glue on the bottom and then just attach it to you your surface.
And to flatten, you'll wanna retract your blade all the way up before you do this, but everything should be in the plane, don't take it apart. Keep it all in there and you're just gonna rub it across the surface of the board like this. And what that does is start to flatten they high spots on the bottom of the sole. So, you'll see your progress. You'll start to see some shiny areas and some rough areas and, of course, those rough areas are the ones we're trying to get down.
And now if I wanted to keep going, I would and get it perfectly flat. And you can work your way up to a different grit. You wanna get up to, maybe, 1200 or 2000 grit paper if you're working with paper. 'You can also use oil stones or water stones as well. And go up as high as you like. If you get a mirror finish on the bottom of this, that's perfect. If you get close, that's probably good enough.