A-frames - What's That?

I keep referring to Derdesteen as an "A-frame"ing spot. What is that? Well, the picture below is an example of it (note that this picture is not from Derdesteen, although I hope to rectify that at some stage)



It's essentially a wave that is breaking to the left and the right - it rises to a peak at some point, and you can basically choose to go left or right, although your choice might be limited by your exact position (and the power of the wave).

The picture was borrowed from this site