I was reading How to and Why over at classicshaving.com/ and came across this concerning the TPT.

Quote Originally Posted by How To And Why
Touch the razor edge lightly and note the reaction. A dull edge produces no drawing feeling. A razor that has the proper cutting edge tends to stick to the thumb and will not slide along it.
I'm still new to all this, but I've never heard that the edge wouldn't slide at all.