Pica

Hey there all of you... I'm new to this forum so hoping someone can help me out on this one. I have seen some awesome movies and pics from some spectaculair coasters on RCT3. Now I'm trying to build one but I stumble upon a designers question... How can I get the rocks (of any kind) to overlap each other? That way I can make a rocky surface (or wall) without those stupid gaps in between the rocks. I've seen on the movies (eg. Winter Wonderland) that it is possible, yet the maker isn't there to respond. If anyone knows the trick, please do tell Thanks for your time and assistance. PiCa