Granular media, such as sand, will flow like a fluid when sufficiently driven by an external force. Because collisions between grains are inelastic, granular temperature (defined in analogy with temperature as the width of the velocity distribution) decreases with time. Since the speed of sound in a fluid goes as the square root of its temperature, the speed of sound in a granular flow will decrease. Eventually, then, most granular flows enter a supersonic regime; shocks will be endemic. Were port on the formation of shock waves in granular flows. Grains are poured into a quasi-two-dimensional vertical channel and flow downward, accelerated by gravity. Obstacles placed in the channel produce oblique shock waves analogous to those that form near obstacles in supersonic gas flows. Because these shocks are stationary and have a simple geometry, they provide ideal test beds for theories of rapid granular flow.