PSA: When should you or shouldn’t you use a mat or shelf liner for added friction during benching? You should avoid using these mats on newer benches that offer adequate friction alone. If you feel the need to use one of these mats on a brand new bench, you probably need to work on your technique. That is not to say these mats should never be used; there are many benches out there that have been misused already or have just been worn out over a long period of time that you SHOULD use these mats

Transistors - NPN & PNP - Basic Introduction