How can I create custom shapes?

Solution 1:

Short answer: Use Easy Weld instead of Weld.

Long answer:

1. If you haven't yet, no collide the two objects.
2. If you haven't yet, select the Weld tool from the tool menu.
3. On the first object, right click where you want the center of the object's rotation to be.
4. Position your crosshair on the second object. A ghost of the first object should appear for your convenience. If it doesn't, try checking the context menu settings.
5. Once you have the ghost object where you want, hit the mouse button the tool description tells you to.
6. You should be able to rotate the object on an axis now. Rotate it where you want, then hit the mouse button the tool description tells you to.
7. Done! Remember to save the object as a dupe for future use.