My husband takes half of a pill, and I was having so much trouble with the cutter that I bought from the Pharmacy. It would cut the pill, but lots of times it crumbled into pieces instead of splitting it in half. I mentioned this to my Pharmacist, and he gave me this simple, but effective way.
Take about 3 playing cards from a deck, and place them on a flat surface. Using the photos as your guide, place the pill with the dividing mark on the straight edge of the card stack. Next, with your left index finger, hold the left edge of the pill in place while you press the right edge with your right index finger.
This works almost 100% of the time. It will work best if the pill is flat.