> ppww("twill", "2/1", warp = 7, weft = 9)
/ - - - - - - - - - \ 
| X   X X   X X   X | 
|   X X   X X   X X | 
| X X   X X   X X   | 
| X   X X   X X   X | 
|   X X   X X   X X | 
| X X   X X   X X   | 
| X   X X   X X   X | 
\ - - - - - - - - - / 

