As we know when you have a shaped cabinet or part, the shape is not controlled or locked down in any way. This is why we need constraints to control what we want the shape to do.
In the example below I have a cabinet with a 200 x 200 void it the back left corner. The shape has no constraints on it.
If I now change the cabinet from 800 to 600, you will see that the size of the 200 x 200 void will not hold
Rather than using constraints to lock the shape, the old way in previous version was to point lock the shape. This has been re-introduced in version 8.
When you edit the shape with the select tool you can click on the line (as shown below) and you will see the lines start and end positions in the parameters on the left hand side(highlighted).
You will also see a check box which gives you option of where you want the Start X point of the line to be locked to. In this instance I will lock the point the left meaning it will lock it at 200mm from the 0 point. Do the same for the End X point of the line as well.
Now when you change the cabinet size the line should stay 200mm from the left hand side of the cabinet. If you are changing the depth of the cabinet you will need to also lock the Start Y and End Y points of the line to achieve the same result.
Note: This is only an alternative to constraints, and we would use it in certain situations like the one shown above.