A whipping by a cat-o'-nine-tails was a common punishment during the Napoleonic Wars. It was made of rope with knots at the end to scrape the sailor's back. Oftentimes, bits of metal or glass were tied onto the ropes to ensure pain for the sailor. In modern times, the cat-o'-nine-tails is used as a costume accessory.
Unravel the rope into three separate strands starting at one end and stopping about halfway up the rope. Two feet should be in three sections and the other two feet should still be whole.
Unravel each of the three smaller sections into three sections. You should now have two feet with nine smaller strands. These are your nine tails.
Tie three knots into each strand. You can place them all near the end of the strand or you can space them out along the 2-foot length, mixing or matching the spacing on the nine tails.