Filet blanket worked in half double crochet. Length is determined by number of repeat chained for row 1. Overall length and width is determined by the number of rounds done after row 1.
Suggest using a hook at least 1 size larger than the what the yarn ball band calls for to avoid a stiff blanket.
Any yarn can be used that would be suitable for the project you are creating. As with most filet patterns, the filet shows up better with solid colors, but works well with cake yarns with long stretches of the same color.

Scarves can be made from this pattern by starting with a very long starting chain (repeat is multiple of 5 +3 for the chain).
A near square blanket can be done starting with only 1 or 2 repeats for the starting chain.
Long thin lap blankets can be created by making a long starting chain and doing fewer rounds than for a regular blanket.

Gauge is unimportant for this pattern. This and my other free original patterns are available on my Playing With Yarn Facebook page: