Step 1: Make a mark
Place your SIM card next to a ruler and mark where you need to cut with a pencil or pen. Mark the SIM to be 12mm on the shorter side and 15mm on the longer side, using a microSIM as a template if possible. If you can, mark lines to cut the SIM from the bottom and left hand edges for a minimum amount of cuts. Depending on the size and location of the contact area on the card, you may need to adjust cuts to avoid cutting through the metal (see our finished result). Under no circumstances should you cut through the contact area.
Step 2: Trim down
Carefully cut the SIM card down to size with a pair of scissors or a craft knife. You can discard the cut-offs.
Step 3: Cut the corner
Cut the top right hand corner off the SIM card at the same angle as it was previously. Use the off-cut as a template.