While making the invitations to my wedding, we needed a way to draw straight lines in pencil on the envelope quickly and accurately. So I made this crude drawing template. We used a pencil to lightly add lines to the envelope, then would write on the lines in non-smearing ink then would lightly erase the pencil to leave just the addresses.
Note: you do not need to use all the lines, just added them in case you want to have one at the top to know how tall to make the top one. Look at the photo for what I mean.
The author marked this model as their own original creation.