Secure the wood bat in a mounted vise, and tighten the vise to immobilize the bat.
Drill a 1-inch wide hole in the large end of the bat, making the hole as much as 8 inches deep. Remove the bat from the vise.
Cut a 1-inch diameter dowel 1 inch long with a small saw.
Drop 1-inch diameter corks into the bat cavity you created. Leave enough space for the 1-inch long dowel to fit in and plug the cavity at the bat's end.
Put white household glue on the inner area of the bat cavity where the dowel plug will go as well as on the sides of the dowel plug.
Push the dowel plug into the end of the bat until it is flush with the tip of the bat. Allow the glue to dry thoroughly.
Sand the end of the bat with sandpaper until it is smooth. Use the sandpaper grit of your choice, depending on how much you want to refine the area. For general smoothing of the bat end, choose a medium-grit sandpaper of about 100. Use successively higher grit sandpaper for finer finishes.