Walmart offers the Planket Plant Frost Blanket and Cover 5" Spike 14-Pack for $2.60. Opt for in-store pickup to dodge the $5.99 shipping fee. (Amazon charges a few cents more with orders of $25 or more.) That's $5 off and the lowest price we could find. They can be used with the 10x20-foot rectangular Planket, which is manufactured with 14 built-in metal grommets.