Phil is probably right. Mocket sells a product called a "multi purpose stand off". They sell accompanying threaded rod these "caps" screw onto. They have various rods - some fit into "barrels" which need to be counter sunk either with an interference fit or using construction adhesive. Or they sell versions that are like a lag on one end and fine thread on the other (which requires a special tool for installation). You'd drill the panels to slide over the rod then these stand offs would screw onto the rod thus securing the panel. Here is a link to the product I believe they're using http://www.mockett.com/supports-signage/multi-purpose-support-hangers/multipurpose-stand-offs-mpb6-mpb11-series.html