23 of course the engaging disengaging portion can be constructed by combining the projecting row projecting portion step portion fitting hole or concave portion appropriately by providing with the engaging disengaging means of the second to fifth embodiments the engaging disengaging means can be constructed with a simple structure in order to avoid formation of a complicated structure further the engaging area between the engaging portion and the engaged portion can be set up appropriately thus a sufficient holding force between components can be secured the engaging disengaging means can be constructed with a simple structure so as to avoid formation of a complicated structure as a result reduction in size and thinning of the entire slider 20 can be achieved and its handling is facilitated fig1 and 15 show another example of the structure of the narrow groove like accommodating concave portion 23 d held above the front end post portion of the pull tag mounting post 21 d the cover member 23 of the sixth embodiment is comprised of right left side wall portions formed on the right and left side of the top wall portion having a smooth convex curve face on its top surface and a front wall portion for joining the top wall portion and the right left side wall portions in the region of the accommodating concave portion 23 d 1 of the cover member 23 the cover member 23 has a substantially fallen c shaped section this accommodating concave portion 23 d 1 is formed up to the front face of the front end post portion of the pull tag mounting post 21 d formed integrally on the top face of the front end portion of.