I'm stuck. I'm at the end in the third trial where you have to get across the cliff. I looked in the walkthrough and I still can't figure it out.
Click your mouse over the centre of the most protruding rock on the other side of the gap or where the big yellow 'X' is on the diagram below. Hopefully Indy will make his way safely across to the other side, and then you've made it... almost.
http://lastcrusade.mixnmojo.com/pics/grail3.gif)