Time to tie: Less than 1 minute
Rope used: One 15 ft rope

Imagine you are tying a loop around your thigh and now want to continue tying in a downwards direction where the rope is perpendicular to the loop you just created. There are several options for you to perform this task while making sure the loop is kept in place:
As you can appreciate, in Shibari, there are several options to keep the ropes in place. Frictions are the answer to the conundrum between option 1 and option 2. "Frictions" is used as a blanket term to refer to the use of taking advantage of the rope's natural friction-creating ability to keep the ropes in place by tying it around itself. Frictions are quick to tie, easy to untie, and will remain solid under tension.
There are plenty of ways you can tie frictions. The one you use really depends on your personal preferences and what you want to achieve. In the case of the X-Friction, it is a great choice for when you want to attach ropes that cross each other in a T-shape.
Have fun tying!
Eve