Abstract: A guard fence system is useful for preventing persons from falling off bleachers. The guard fence system comprises at least two upright posts mounted to the bleachers. Each post has a lower U-channel and an upper U-channel spaced a predetermined distance apart. The lower and upper U-channels have respective slots that open into the top ends of the U-channels. A guard fence member comprises a rectangular frame covered with a grill material. Upper and lower pins extend oppositely from the frame vertical members. The lower pins of the guard fence member are inserted into the slots of the lower U-channel. The guard fence member is pivoted to a generally vertical attitude such that the guard fence member upper pins are proximate the upper U-channels on the posts. The guard fence member is lifted and further pivoted until the upper pins thereof are vertically over the slots of the corresponding upper U-channels on the posts.