Hi Jakub,
You can check for any clearance using the Clearance tool in the Prepare tab of SpaceClaim. This will show faces that are very near but not touching. After you recognize the bad faces you can use the pull tool to extrude the faces so they come in contact. You can choose the Upto (U) option in the Pull menu to pull any of the faces to the adjacent face on the other body.
You are navigating away from the AIS Discovery experience