On your Circular Sock Machine, a small heart is a nice way to use scrap yarn from making socks.
The heart is completed on the machine except for grafting together the beginning and ending stitches, as in closing a toe of a sock.
Uses for such a cute little heart include:
Use flat for a coaster
Enclose in a greeting card or note to send love
Fill with rice, heat in microwave for 20-30 seconds = Hand Warmer
Place in the freezer for a Boo Boo Cooler
Include in Valentine decorations

The pattern includes directions for a small and large heart as knitted on a 60 cylinder. If using an 80 or 72 needle CSM, your heart can be made larger by using a full half of the needles and increasing the rows between bottom and top by 2 more rows.
If filling with rice, either keep your tension tight or line with tee shirt type fabric.
Tension that is slightly less tight makes just as cute of a product with a little more ease of operation on the CSM.