A base member for cooperating with a support member and at least one fixing member to form an anchor assembly mountable to a form board on which wet concrete may be poured during formation of a concrete substrate, the base member comprising: a mounting portion for positioning the anchor assembly on the form board prior to inserting the fixing members into the form board; an aperture having first and second generally opposed ends, the first end being open to facilitate insertion of the support member into the aperture; and a barrier reconfigurable in use from a first configuration, in which the barrier restricts ingress of wet concrete into contact with the support member via the second end of the aperture, to a second configuration in which the barrier allows an object to extend via the second end of the aperture into contact with the support member.