Automatic contacts are detected during the simulation, without your taking direct action to detect them. If you want to see them before running the simulation or evaluate any that are detected, run the Automatic Contacts command.
To detect contacts, click Automatic Contacts 
in the Contacts panel.
The model is evaluated and contacts added. The faces must satisfy two criteria:
- The distance between the faces must not exceed the Tolerance value as expressed in the Simulation Properties.
- The angle between the faces must be within 15 degrees of being parallel.
When automatic contacts are generated, geometry decoration for mixed (solid + shell) and pure shell displays in browser indicating the type of contact. There are 3 possible types:
[E-E] Edge-Edge, contact created between two edges
[E-F] Edge-Face, contact created between an edge and a face
[F-F] Face-Face, contact created between two faces
Access to the Tolerance value and contact type is provided in the Simulation Properties on a per simulation basis. The angle requirement is fixed.
You can change the contact type by editing individual contacts or multi-select contacts and change the selection to another contact type.