To Assign Global Variables to a Solid's Profile

In the Modify Feature toolbox, select the Modify Profile tool.
In the tool settings window, select the Modify DD Profile Parameters icon.
Select the solid and accept with a data point.
The Modify Profile dialog opens, displaying the original profile and the parameters. A list box displays the parameters and their values. As well, the original parameters/dimensions appear on the solid.
In the Modify Profile dialog, click the row for parameter W1.
Click the Equation icon to the right of the W1 field below the list box.
A dialog opens displaying the global variables.
In the list of variables, double-click Width so that its name appears in the input field above.
Click OK to complete the assignment.
Repeat steps 4 to 7 for the W1 and T1 parameters, assigning the Global Variable Length to L1 and Thickness to T1.
Click OK in the Modify Profile to finish.

Finally, you need to assign the Height variable for the solid. This dimension is not part of the DD profile, it is the distance that the profiles was extruded. You can use the Modify Parametric Solid or Feature tool to make the assignment to this dimension.