Connector modules have complementary profiles configured for sliding engagement. Modules bearing a first profile may be mounted in series, such as on a rail, on a frame or component. Modules bearing a second profile may similarly be mounted in series, such as on a rail, so that rails bearing modules with the first profile may slide into rails bearing modules with the second profile. Contacts in connectors of the module are configured to facilitate sliding engagement. Male contacts are biased to protrude, but travel into connectors in which they are mounted during sliding until aligned with corresponding female contacts.