The main reason I use a layer of painters tape is that as Jarhead said, the retention of the knife is at the mouth of the sheath. On smaller 1-5 inch blades one layer has worked best for me. On larger blades like the DF, I have used two layers. If you put too much tape, you end up with the blade wiggling around, but ultimately its up to the end user to determine of that is acceptable or not.