I have a lot of stencils in my craft room. And I find so many of them work well for strings in my zentangle practice. The one pictured here is actually meant for quilters - but it fits so nicely on this tile that I'm sure I'll be doing more with it in the future.
The pens used are the black and sepia Sakura Micron pens - I used the 05 size here. Shading is with a black pencil and a Prismacolor colored pencil.