You can make a standard envelope using a square piece of paper by following these steps from wikiHow :
: Position the paper like a diamond and fold it in half, corner to corner, then unfold it to leave a crease. Fgronov rar
: If you need a more professional look, use glue and scissors to follow step-by-step official envelope tutorials . You can make a standard envelope using a
Could you clarify if you meant (the mathematician), a specific RAR archive file , or something else entirely? corner to corner