The mats in traditional Japanese buildings are known as Tatami. The mats upon which throwing techniques are practised in Jiu Jitsu are consequently also referred to as tatami.

Whenever a student wishes to step into or out of the matted area of the dojo, they must wait by the side of the mat until they are given permission by the most senior grade on the mat to step onto or off the mat. When awaiting permission, the jitsuka should wait in a su dachi style position, with feet together and hands by the sides or with hands cupped in front of him. For a busy mat it may be necessary to attract the senior grade's attention by simply raising an arm - as though asking a question.  The senior grade will give his permission by performing a standing bow to the jitsuka wishing to enter or leave the mat. At the same time, the jitsuka should perform a standing bow back to the senior grade.

In some instances the most senior grade on the mat may be a novice and the club instructor must then wait for permission from the novice to enter onto the mat. Of course it is polite to let your instructor on in good time or else you may find a session "particularly active" due to your inaction.

The bowing on and off the mat serves a practical purpose in this case. Whoever is the most senior grade on the mat is effectively in-charge of the mat, and thus the safety of everyone on the mat is their responsibility. Therefore it is in the best interests of the senior grade to know who is on and who is off the mat. The senior grade should be particularly aware of why students are leaving the mat.

For example should a student have received a knock on the head and simply head off to the changing rooms to take a look at the newly forming lump, they could fall unconscious. Therefore the senior grade should firstly be informed of why the student is leaving the mat - and in this instance send another student with them to keep an eye on them. Both students would then be given permission to leave the mat.

This piece of etiquette can extend a little further based on these grounds (and hopefully common sense). Many dojo are almost fully matted, but not all. It may be that some off the mat training is going on during a session. If someone needs to leave the dojo, they should seek the permission of the senior grade to leave.  Again emergencies (medical, fire alarm, etc.) may affect the exact procedure, but common sense, safety and courtesy (CSSC) should be the three things in mind whenever such a situation occurs.