I have grown around filet crochet because my grandma was a master at it. She mostly made tablecloths and runners -some of which you may have seen in my pictures - I always have her crocheted tablecloths on my table.
Filet crochet is a type of crochet where you make a grid filled with various designs - from flowers and animals to texts and geometric shapes.
It mostly uses two stitches -the chain stitch and the double crochet. Monotone (predominantly white or ecru) crochet thread made of mercerized cotton is used for filet crochet to make window curtains, tablecloths and runners, placemats and coasters and clothes, although nowadays more colors are brought to it.
I have composed a board where you can find filet crochet diagrams and instructions how to filet crochet, interesting designs and free patterns.