An angle adjustor includes a fixed member, a movable member, a plurality
of friction plates arranged between the fixed and movable members, and a
bolt connecting the fixed and movable members. The fixed member and the
movable member each have a notch for receiving a pressing member that
presses the friction plates against the surface of the notch. Each
pressing member is fixed to the fixed member or movable member in a
direction substantially parallel to the axis of the bolt. The friction
plates are fixed between the notch and the pressing member.