Positioning I use:
the tip of my left foot is touching these positions
![](http://i.imgur.com/nIZl9Eh.jpg)
edge of rock / edge of wood beam/ middle of wood / slightly to left of wood
the tip of my left foot is touching these positions
![](http://i.imgur.com/nIZl9Eh.jpg)
edge of rock / edge of wood beam/ middle of wood / slightly to left of wood