An attachment structure 100 for securing a robot arm to a support structure. The attachment structure 100 comprises a mount 104 for mounting to the support structure and a carrier 106 for connecting to a base of the robot arm. The carrier 106 comprises: a rotational alignment feature 300 for engaging a complementary rotational alignment feature on the robot arm base； an axial alignment feature for engaging a complementary robot arm base axial alignment feature； and a locking mechanism to constrain the location of the robot arm base along an axis of the carrier 106 relative to the carrier 106. Also a surgical robot with a robot arm base connected to an attachment for a surgical instrument via articulated links. The robot arm is suitable for securing to a support structure via a carrier 106. The robot arm base comprising a rotational alignment feature for engaging a complimentary carrier rotational alignment feature 300； and an axial alignment feature for engaging a complimentary carrier axial alignment feature. Described in terms of surgical robots that can be quickly relocated from one position to another in an operating room.
