The cutter has a symbol on the top surface plunger to show the way you need to insert the sim card.
You can also look underneath which shows you where the corner cut of the sim card should be oriented.
It cuts very well but you need to be careful that it doesn't cut the chip
Some sim cards have awkward places where the chip is - some on the edge of the sim card.
To avoid this:
- Insert the card in the cutter and look underneath and determine the side that has too much plastic.
- Remove the card and use a pair of scissors to cut away a small excess of plastic.
- Re-insert the sim card in the cutter, look underneath and move it around to get the chip centre of the cutter hole.
- If it's okay, cut away, but if not, just keep cutting small slithers of plastic until you get the chip centred.
Hope this helps.