Save those old gift cards and promotional cards that you get in the mail. The ones that are the size of a credit card work very well. Take a rigid plastic card and gently wind duct tape around one end. Be sure that the duct tape is at the very edge of the card. Continue winding the duct tape around the card until the tape is about 3/8″ to 1/2″ thick. The tape will cover about 3/4 of the card.
Wrap two rows of electrical tape around the remainder of the card. I use one row of black tape and one row of red tape (for higher visibility). When finished the card will contain about 9′ of duct tape and about 24′ of electrical tape. Store tape in a zip bag or other plastic wrapper because the glue can seep out over time and create a sticky mess.
Winding and Lengths
When winding tape on the card initially the first 15 winds equal about 3′ of tape. Each wind is one face of the card. The next 3′ of tape take about 14 winds. The next 3′ take about 13 winds. My tape card has about 9′ of duct tape and about 12′ of each type of electrical tape. The tape card has a total of about 33′ of tape (9′ duct tape, 24′ electrical tape). These tape cards pack a lot of tape into a very small and flat package.