16. This opens the Parameter Properties dialog box where the parameters are defined. Make sure Family Parameter is selected as the parameter type, give the parameter a descriptive name and choose Instance as the type of data. We prefer not to use spaces or hyphens in the Name field as they can result in errors when computing values in tables.
17. Click OK to create the parameter. The parameter replaces the dimension in the view and has a default value the same as the dimension.
18. Repeat steps 15-17 for the remaining dimensions, including the dimension in the Plan view. Be sure to select Instance every time; each time the Parameter Properties dialog box is opened, the Type option is selected by default. In this case, both legs are to maintain an equal length so a dimension is added to the other leg, then, with the dimension selected, the same parameter is selected from the drop-down list. When that parameter is modified, the length of both legs will change.
19. Save your file then click the Load Into Project button to load it into a new or existing Revit file.
20. In the Project Browser, select the clip type and drag it onto an existing face in the Revit file. Move your cursor over another face to create a second clip; the base of the clip aligns automatically with the face that your cursor is over.
21. Select each clip then adjust its parameter values, for each clip independently, in the Properties dialog box.
As you can see, with a little forethought and planning, you can easily make an adjustable, parametric clip that can meet many of your modeling needs.