For example, all elements that belong to the Desk family have a Width property, but its value varies according to family type. Thus every instance of the 60” x 30” family type within the Desk family has a Width value of 5’, while every instance of the 72” x 36” family type has a Width value of 6’.
A common set of instance properties also applies to all elements that belong to a particular family type, but the values of these properties may vary according to the location of an element in a building or project.
For example, the dimensions of a window are type properties, while its elevation from the level is an instance property. Similarly, cross-sectional dimensions of a beam are type properties, while beam length is an instance property.
Changing the value of an instance property affects only the elements in your selection set, or the element that you are about to place. For example, if you select a beam, and change one of its instance property values on the , only that beam is affected. If you select a tool for placing beams, and change one of its instance property values, the new value applies to all beams you place with that tool.