The author seeks to show what conditions must be fulfilled by rail fasteners for use in slab track. Vertical elasticity has to compensate for the resilience of cross ties on ballast, and elastic restraint in other modes of deformation is discussed. Considerations of noise and vibrations raise problems of damping which must influence the design of elastic elements. Requirements for adjustability during installation and later maintenance are important aspects of practical design having repercussions on cost and line occupation. Where slab track is proposed for very high speeds, fine adjustment becomes essential. Some desirable features of practical design are indicated.