Start by painting your nails in a base colour and wait for it to dry
Now take 2 pieces of Sellotape and stick them together so there is a pyramid shaped gap at the bottom.
Then place the Sellotape on your nail with the gap at the bottom and paint the second colour over the gap.
Carefully peel the tape of, you should end up with a triangle at the bottom of your nails.wait for the triangle to dry before you follow the next step .
Repeat this process at the top of the nail, if all goes well you should end up with nails that have sand timer thingies on them! TA DA!!! P.s. your nails will turn out much better than mine.