Known in the US as Triple Crochet (tr)
yoh twice, insert hook into 3rd chain from hook, yoh again.
draw yarn through chain, yoh again. 4 loops on hook
draw through first 2 loops on hook, yoh again. (3 loops left)
draw through next 2 loops on hook, yoh again. (2 loops left)
draw through last 2 loops on hook.
repeat in the rest of the chains.