Collect two bottles that are the same size. Remove the lids from the bottles. Cut or drill a small opening in one of the plastic bottle lids, big enough for the salt to run through. Screw the lid back onto the one bottle.  Fill the bottle without a lid with dry sand or salt. Place the filled bottle on a level surface and place the one with the lid on top of it, for the heads to meet.  Use white sticky tape and taping the two bottles together from the bottle necks to the heads. Use your hour glass as a decorative object.