Parts in assemblies that fit together must frequently change size to accommodate design changes. When creating a part in-context of an assembly, you can project edges, loops, faces, or sketch geometry from one part into the sketch of the current part. The cross-part sketch geometry can be used to constrain other sketch geometry or to create a feature. Cross-part sketch geometry is adaptive and automatically updates when the parent part changes.
For example, an assembly has a part with a sleeve that fits over a shaft on another part. You can project the shaft end into the sketch to represent the inner diameter of the sleeve. You extrude the profile to create the sleeve extrusion. The sleeve is adaptive to the shaft and automatically updates to changes in the shaft diameter.
The size and position of the cross-part sketch is based on the parent part. A cross-part sketch can be used like any other sketch geometry to create a feature in the new part.
The cross-part geometry is listed in the browser with a Reference sketch symbol 
. The geometry, sketch, and part are adaptive 
.
Use the Cross part geometry projection options to control whether projected geometry is associative. Click 
OptionsAssembly tab. Under In-Place Features, select the check boxes for Cross part projection to enable associativity when the geometry is projected.
You can break the link between a part created using a cross-part sketch and its parent. In the assembly, activate the part. Expand the part in the browser, right-click the sketch, and then select Break Link. The parts are now independent of one another.
You can control the adaptivity of the projected geometry, the sketch, or the part. Use the context menu to control adaptivity.