In a complex assembly, it can be difficult to visually determine whether components interfere with each other. With Interference Detection, you can:
Determine the interference between components.
Display the true volume of interference as a shaded volume.
Change the display settings of the interfering and non-interfering components to see the interference better.
Select to ignore interferences that you want to exclude, such as press fits, interferences of threaded fasteners, on so on.
Choose to include interferences between bodies within a multibody part.
Choose to treat a sub-assembly as a single component, so that interferences between the sub-assembly's components are not reported.
Distinguish between coincidence interferences and standard interferences.
To check for interferences in an assembly:
Click Interference Detection 
(Assembly toolbar) or Tools,
Interference Detection.
Set options and settings described below in the PropertyManager.
Under Selected Components, click Calculate.
The detected interferences are listed under Results.
The volume of each interference appears to the right of each listing.
Under Results, you can:
Select an interference to highlight it in red in the graphics area.
Expand interferences to display the names of the interfering components.
Right-click an interference and select Zoom to selection, to zoom to the interference in the graphics area.
Right-click an interference and select Ignore.
Right-click an ignored interference and select Un-Ignore.
Components to Check. Displays components selected for the interference check. By default, the top-level assembly appears unless you pre-select other components. When you check an assembly for interference, all of its components are checked. If you select a single component, only the interferences that involve that component are reported. If you select two or more components, only the interferences between the selected components are reported.
Calculate. Click to check for interferences.
Displays the detected interferences. The volume of each interference appears to the right of each listing. When you select an interference under Results, it highlights in red in the graphics area.
Ignore/Un-Ignore. Click to switch between ignored and unignored mode for the selected interference. If an interference is set to Ignore, it remains ignored during subsequent interference calculations. See Show ignored interferences under Options.
Component view. Displays the interferences by component name instead of interference number.
Treat coincidence as interference. Reports coincident entities as interferences.
Show ignored interferences. Select to show ignored interferences in the Results list, with a gray icon. When this option is cleared, ignored interferences are not listed.
Treat subassemblies as components. When selected, sub-assemblies are treated as single components, so interferences between a sub-assembly's components are not reported.
Include multibody part interferences. Select to report interferences between bodies within multibody parts.
Make interfering parts transparent. Select to display the components of the selected interference in transparent mode.
Create fasteners folder. Segregates interferences between fasteners (such as a nut and bolt) into a separate folder under Results. See Interference Detection with Fasteners.
Displays non-interfering components in the selected mode:
Wireframe
Hidden
Transparent
Use current. Uses the current display settings of the assembly.