U.S. President Barack Obama's visit to Japan last month triggered a barrage of security measures in Tokyo. Lockers and garbage cans at major train stations were taped shut and throngs of solemn-faced police officers appeared to be everywhere.

During this weeklong period of tightened security, the police also beefed up the use of one of their more controversial tools: "shokumu shitsumon," or police inquiries.

Here are some questions and answers about the routine commonly referred to as "shokushitsu."