This is for the one week fridge magnet challenge.
Took about 1 hour.
Step 1: Get materials
sharp razor blade
I got the magnet sheet at Princess Auto (Canadian tool store) for 10 bucks. It is 1.5 mm thick and has an adhesive backing on one side.
Step 2: Draw out tetrominos
My squares were all 1/4" square. I made a square 6" square and tried to get as many of each shape onto the grid paper with out wasting space. My pattern worked but I am sure there are more combinations of ways to get the tetrominos on the page.