Weld Tool in Version 5
Step One, using the shape tool, draw a circle and a square separate from each other.
Step Two, using the select tool, click and drag one of the objects so that it overlaps the second.
Step Three, with both objects selected click on the Weld tool to open the flyout, and click on basic weld. The objects are now welded together.
The XOR weld tool allows the intersecting portions of each object to be welded to the other object so that indentations are left on each.