These are the things you'll need:
White nail polish
Black nail polish
A really thin nail brush
and a top coat (I really like when it's a matte top coat but you choose).
Step1: Start by applying a coat of white nail polish.
Step2: When that has dried start making lines with the black nail polish (2a,b,c) by using the thin brush.
Step3: Fill in the triangles with the black nail polish. I use the thin brush here too because it's not so messy.
Step4: Let that dry and then Finnish of by using the top coat!
You can follow me on: