Polaroid format, despite having so many years, is very used in decoration.
The measures for a real Polaroid are 8,8 cm wide and 10,7 cm high.
Draw a rectangle in the black side of the sheet and cut it.
The above and side margin is 0,6 cm and the bottom is 2,2 cm, so draw another rectangle inside and hewn with the cutter.
We already have a Polaroid frame ready for use it on magnetic surfaces.