У вашего броузера проблема в совместимости с HTML5
SRT climb, work & DdRT descent.
Demonstrating the Super Smooth (ring&ring) and the Hitch Hiker 2.
The HH2 works equally well for both SRT & DdRT. In fact, there is negligible difference in feel & function with either technique when using the HH2.
Both the Super Smooth and the Hitch Hiker 2 are available from TreeStuff.com
Chris Coates gave me the concept "Single Up - Double Down".