Molecular modeling constituents having plug ends are joined by a coupling having a connective sleeve and a locking sleeve. The connective sleeve receives a plug in a bore at each end thereof. Radially deflectable staves of the connective sleeve have ridges on the inside surface thereof for engaging corresponding annular grooves about the circumference of the plugs. A locking sleeve fits over the connective sleeve and allows outward radial deflection of the staves in an OPEN position for insertion/extraction of plugs into/from the coupling, and inhibits radial deflection of the staves in a lock position to prohibit insertion/extraction of plugs into/from the coupling. The OPEN and LOCK positions are relative rotational positions of the connective sleeve and locking sleeve.
