- Lay your sheet of paper flat.
- Orient it so that it's portrait - so the shortest side is towards you, and it's "long" stretching away from you.
- Take the top-left corner, and pull it down and towards the right side. Don't crease it yet.
- Your aim is to pull it down and gently press with your left hand. You want to crease the page in such a way that it forms a straight line from the bottom-left part of your fold to the top-right part of your page. Now you will have a triangle, with a bottom part sticking out toward you.
- Take that bottom flap and fold it up as much as you can without folding part of your triangle.
- Crease that bottom flap well. Turn your page over and fold that flap the other way and crease it again.
- Carefully tear that bottom flap off.
Un-fold your triangle. It's now a square.
without a crease ∞
It's possible to create your square without a crease running through the middle.
To do that, you'd have to be very careful about creating your triangle just enough to figure out where your bottom flap would be.
without holes ∞
If you're using paper with holes in it, and you don't want the holes in your square, there is hope!
When you fold your triangle flap over reach for the un-holed long side and fold it towards the holed side. Don't put your corner right to the edge, but to just before the holes.
Now when you create your square, you'll have a second flap to get rid of - the flap with the holes.
Note that when you do this, your square will be smaller than it would have been with the holes.