An umbrella includes: a spring catch secured on an upper portion of a central shaft of the umbrella, and a runner slidably held on the central shaft to be engaged with the spring catch when opening the umbrella, with the spring catch juxtapositionally positioned and operated outside the central shaft without cutting a catch slit or slot through a tube of the central shaft as found in a conventional umbrella having the spring catch retained within the central shaft and protruding outwardly through the catch slit for locking the runner, thereby enhancing the strength of the tube of the central shaft and prolonging the service life of the umbrella.