An instrumentation set may include insertion instruments for forming an implant between bone structures. The insertion instruments may include a spreader and a separator. The bone structures may be vertebrae. Implant members may be attached to the spreader and positioned between the bone structures. The separator may be inserted into the spreader to establish a desired separation distance between the implant members. Connectors may be inserted into the implant members to join the implant members together and form the implant. The insertion instruments may be removed. A seater may be used to set the position of the connectors relative to the implant members to inhibit disassembly of the implant.