The other day I was looking for an envelope to put my rent check in so I could slip it under my landlord’s door, but I was all out. I didn’t want to go buy a new box, so I took an old envelope from a Christmas card and carefully unfolded all its edges so as not to rip the shape. I traced that envelope’s shape onto a thin piece of cardboard and created a template for all my future free envelopes.
In the image above you can see that I used an old calendar from the Red Vic on Haight. [Note: the Red Vic calendar is good for rent check envelopes because it’s free and looks cool, but I don’t recommend for mailing purposes due to the flimsiness of the paper].
All you need to do is make a couple of neat little folds and use some Scotch tape to attach the edges. Insert a rent check [or anything else you’d like to mail] and seal up the envelope.