Unlike normal things in Second Life, walking on the rocks usually leads to unusual results. You can either find yourself walking *in* the rocks:
or walking in the air *over* the rocks:

This is because the rocks are "sculpties": odd prims in the Second Life system, and sculpties don't know where their boundaries are. The physical boundary, the surface that you walk on, is different than the visible boundary, the surface that you see. This leads to the odd efects.
We're now using these sculptie rocks more and more on the islands of New England, and we've begun to use "megaprim" (huge monster prim) sculpties, which can magnify the problem. They look wonderful and they vastly lower the number of prims needed, but they're not much fun to walk on.
If you'd like to have one of the rocky areas of your parcel suitable for walking on, here's what to do.
The first step is to make the rock you want to walk on "Phantom". This means that the rock will have no physical boundary at all!... you'll walk right through it! "Edit" the rock, go to the "Object" tab, and check the box that says "Phantom".
Now you can walk right through your rock. Of course, that's not what you want either, but at least the rock is not forcing you up into the air when you try to walk over it.
The goal now is to create an invisible prim surface from a "normal" prim that you can actually walk on, and then set it up in such a way, into the surface of the rock, so that by walking on *that* invisible prim it looks like you're walking on the rock. Do it first with a visible prim. Let's say you have a flattish rock with a rounded front edge. Make a cube prim with roughly the area of the flattish rock and sink it in so the surfaces are almost the same. Then take a cylinder prim and stretch it and angle it in such a way that it corresponds to the rounded front of the rock; and sink it in too. Nothing precise here... you're just looking to make the surfaces approximately the same.
With those in place, you'll find you can walk on the rock naturally. The only problem is that those plywood prims look ugly.
So, next, take a "fully transparent" texture and apply it to the two plywood prims. You may have a transparent texture in your Inventory; if not, I've placed a free full perms copy in the Land Office for you to take. Edit the prim, go to the Texture tab, and drop the "transparent" texture into the Texture box on that page. The prim will disappear!
But it's still there. If you need to see it to move it or modify it, use the View Menu and click on Highlight Transparent, which will cause everything thats transparent to turn red. You can see your "invisible" prims easily. Click on the Highlight Transparent again to turn off the red.
So.... now you have a nice rocky area that you can walk on naturally. Questions.... ask me or Ceorl Onlyone.
Sudane................................