Gridder SpoolPerfectly lays out rows on a growing bed to give each plant the ideal amount space. Many plant spacings can be achieved with one spool using the corners, sides, and the middle of grid squares. We have spools for 24, 30, or 40 inch wide beds. Each unique bed width Spool requires it own handle matched to the same bed width. Example A 24" (GDR24) handle can be used with any 24" (GDR24) Bed Spool. A 30" Handle cannot be used with 24" or 40" bed spools.