Abstract: A tablet holder includes a generally square base having a protuberance formed in each side of the base, each protuberance extending radially outwardly with respect to a center of the base. Each protuberance is recessed relative to the base, creating a channel having a bottom wall and upstanding sidewalls. A detent plate is mounted in each channel and has a range of travel relative to the bottom wall. A raising and lowering assembly raises and lowers the detent plate. Guide rails are formed in each channel and a holder is slideably mounted to the guide rails. Each holder has a slotted bottom plate, guide rail housings for slideably receiving the guide rails, on opposite sides of the slot, and an upstanding end wall adapted to abuttingly engage a tablet. Each holder is slideably adjustable or locked against sliding when the detent plate is elevated or lowered, respectively.