Yep, we slide our knees through the corners. The material is usually a high density plastic or leather. It depends on rider preference as both a have different grabbiness to them.
I had to temporarily retire this last year due to finances (just had a son and two very expensive high speed 140+ mph wrecks set me back with repairs and injuries), but it looks like I may have a endurance racing ride lined for next year which would be just the thing to tide me over until I can afford to start racing again.
Sad thing is my 600cc race bike made more horsepower at the wheel than my Protege. Lots less torque though.