The front desk at the ACSR building checks student ID's for entry.
For special events and seminars, arrangements are made so that visitors can enter without ID. Just tell them that you are with the Aikido group and they will let you enter.
When there is no special event planned, you may be required to buy a day pass for $10. Any of the teachers or Stanford students in the club can sponsor a pass for you. Class is held in the room right by the front desk, so you should be able to flag someone down from there.
Please make sure to fill out a waiver if it is your first time practicing with us. You can download one here or get one from the instructor.
For location and parking information, look here.