Go to the Portal and click 1 0 0.
At the bottom of the tower, go right 3 screens and into Storage Unit 33/2. Assuming you have all 4 Loop Stabilisers in order to enter Level X, scroll through the rooms until you find a gray 5x5 grid, which has the corner squares.....missing.
OK Osmking, that should be enough info for you to meet your goal. If not, I also teach Remedial Classes (haha) in solving the countless puzzles in the SubVerse, if you ever need any help in the future. I enjoy helping others who are stumped, so don't hesitate to contact me.
SDRanger (Profile also found on Submachine Wiki)