Rail Buttons & Launch Lugs
Until a model rocket is moving fast enough for the fins to guide the rocket, a model needs rigid guidance to stay pointing in the right direction. Rail buttons and launch lugs provide that critical guidance by allowing the model to slide along a launch rail or launch rod for 3 or more feet. Rail buttons are better for heavier models, since launch rails are more rigid than launch rods. But for small models, launch rods are adequate. Depending on the size of the model a launch rod may be 1/8 inch, 3/16 inch, or 1/4 inch or more.