knee sliders 

Formed pieces of hard plastic or compressed leather incorporated onto motorcycle roadracing suits to protect the suit leather from damage while cornering. The sliders are attached to the leather suit towards the outside and just below the knee area of each leg, usually with velcro.

Expert motorcycle roadracers must replace their knee sliders quite often.

knee sliders by razer December 26, 2006

knee slides

Running as fast as you can and sliding on your knees. This is something you would do after getting with a hot girl or getting yourself a girlfriend

She's so hot I did knee slides when I kissed her

knee slides by Green Stuff 91 April 6, 2016