Multiply > Duplicate > Place Mesh - Place Mesh is a tool to place background objects onto the foreground object’s polygons, aligned to their normals. It can work with a single background object or multiple, and placed meshes can be scaled or rotated as they are placed. If multiple background objects are used, they will be randomly chosen among.
The Ignore Placed Meshes toggle will not allow the placement of background meshes on anything other than the foreground object, avoiding placement of meshes on meshes on meshes, and the Use Smooth Normals toggle will place background meshes using a smooth normal setting to ensure better alignment with organic surfaces.
The Populate button creates a clone for each normal of a group of selected points or polygons, depending on the selection mode. Use Random Pitch, Random Heading and Random Scale to randomize these clones.
Naked points can also be clicked on and meshes applied to them and vertices in geometry will be snapped to. The snap behavior can be overridden by holding down Shift.
PlaceMesh cannot use layers from a different object as background layers. The solution is to temporarily copy the layers you require into the foreground object.