Property of surgical site capable of maintaining a space under a membrane for the purpose of guided bone regeneration (GBR). This may be provided by (a) defect morphology in either three‐wall or two‐wall defects; (b) use of bone grafts or substitutes to support the membrane; (c) membrane itself, which is rigid and stable enough to maintain a secluded space below; (d) using a reinforced membrane to avoid membrane collapse.