STEPS TO KNIT A FOOTBOARD WITH GRANNYS:
Start by making a chain long enough to cover your mattress. Be sure to leave some slack so the footboard doesn't fit too tightly.
Start knitting grannys following the desired pattern. A granny is made up of a circle of 3 chains (magic ring) that are counted as the first treble crochet, followed by a group of 3 treble crochets in the same space, a pair of treble crochets at each end of the treble crochets. from the previous granny, and so on. It is important to mention that there are many variations in the patterns of grannys, and in the size of them, it is important to follow specific patterns to achieve the desired result.
Continue knitting grannys until the entire length of your chain is covered. Be sure to join the grannys at the end of each row to avoid leaving gaps in the footboard.
Once you have covered the entire length of your chain, finish with a row of single crochets and close the thread.
Use a yarn needle to hide loose threads.