When building Revit families, it´s quite useful to be somewhat in control of the user inputs... for instance, doors come at certain width´s, it could be 810, 910 ,1010 mm´s or 3-0"´, 3-6", 4´-0" etc. You´ll need a few parameters: User Dim (Length) - What the end user is gonna use
Free CAD and BIM blocks library - content for AutoCAD, AutoCAD LT, Revit, Inventor, Fusion 360 and other 2D and 3D CAD applications by Autodesk. CAD blocks and files can be downloaded in the formats DWG, RFA, IPT, F3D. You can exchange useful blocks and symbols with other CAD and BIM users.