A releasable key arrangement for an edgeboard connector includes a support member having a bore extending completely through the support member. A polarizing key is mountable to the support member. A threaded retaining member is normally mounted in the key and threadedly connectible to the support member...http://www.google.com/patents/US4277126?utm_source=gb-gplus-sharePatent US4277126 - Releasable key arrangement for an electrical connector
