Abstract: An improved means for securing planking to a horizontal support in a platform having a plurality of vertical support frames laterally joined with cross braces for use in constructing bleachers, risers and stages. The vertical support frames have horizontal supports for planking and means are concealed within the underside of the planking to prevent the planking from uplifting or shifting from end to end or back and forth on the horizontal support. The means are in the form of male and female mating endcaps for the planking in cooperation with a hook provided on the horizontal support.