A simple but smart way to use a piece of writing paper as its own envelope.
(Apologies for the not-so-great-quality photos: the only digital camera I have is the one on my phone, and stupidly it doesn't have a zoom function.)
Step 1: Step 1
Get your piece of paper (you can use any size for this - the paper I used for these photos is A4) and put it so that it's portrait (rather than landscape).
Step 2: Step 2
Fold the top left hand corner down to meet the right hand side of the paper (as shown in the picture).
Step 3: Step 3
Fold the lower left corner up, as shown in the picture.
Step 4: Step 4
Fold the upper right hand corner of the paper down so that the edge that forms the long side of the triangle is lined up with the horizontal edge from the fold in step 3..
Step 5: Step 5
This is the point where you can decide how tall or short you want your envelope to be. Fold the lower right hand corner of the paper up and across accordingly (as shown in the picture). Make sure the fold is parallel to the long edge opposite it (you should end up with a rectangle).
Your fold needs to leave a small triangle hanging over the edge (as shown in the second photo). This triangle will be used to seal the letter closed.
Step 6: Step 6
Fold the little triangle over the edge, then turn your paper over: you should have an envelope that looks like the final picture. Use your stamp to seal the triangle down and write the address. Your letter is now all ready to send!
Step 7: Not a step, but an extra photo
This photo shows how your sheet of paper should look if you unfold it at the end. The solid lines show valley folds (ones that dip down), the dotted lines show mountain folds (ones that stick up). If you made a mistake at some point, hopefully this diagram will help you figure out what went wrong where.