1. Knit the hats following the pattern below:
Cast on 36 sts.
Divide evenly over 3 needles slipping purlwise, join in the round.
Rnd 1: [K2, P2] 9 times. Place marker.
Rnd 2: P.
Rep last 2 rnds 8 times. Cast off in rib.
2. Take one of the knitted hat pieces and turn up the ribbed brim. Then at the cast on edge, thread up the tail end and work a running stitch all the way around. Pull up the stitches to create the hat shape, and secure the end.
3. Make small pompoms. Sew a pompom securely in place at the top of the hat to hide the stitching.
4. Sew on a loop of yarn at the top of the bobble for hanging. Thread the completed hats onto a length of ricrac to make a garland.
5. For an advent calendar, make 24 hats; embroider each with a number (1 to 24) worked with yarn, or use a marker to write the numbers onto 24 wooden pegs and attach to a length of ribbon.