Remember that "some assembly required" coffee table that adorned the living room of your first apartment? If you're like many of us, you still have it sitting in the furniture limbo lounge, that place where we put old tables and chairs that aren't worth selling, but are still in good enough shape that it would be a shame to throw them away. You're on your own dealing with the other stuff, but you can give the coffee table a productive second life by turning it into a sand and train play table for your kids.
First buy the train table board that will sit atop your play table and serve as the cover to the sand box. The train table board determines the size of the play table. Train tables are available at most toy stores and have inserts that form the play surface. Make sure you get one that is longer and wider than your coffee table. Measure the length and width of the board, then have your local home improvement store or lumber yard cut a 3/4 inch A/C or A/B grade plywood 1/2-inch longer and wider than the board.
Attach a length of furniture-grade 1x4 along each of the plywood's long sides. Each piece should protrude 1/2 inch beyond the end of the plywood, and the bottom edge of the 1x4 should be flush with the bottom of the plywood. To avoid splitting the wood, pre-drill the 1x4. Next, attach four, 4-inch lengths of 1x4 to the short sides of the plywood at the corners. These short pieces of 1x4 should butt against and be attached to the protruding edge of the long 1x4 pieces.
Next cut two pieces of 1x3 equal to the width of the plywood to form the edges of the sandbox. Use water-proof wood glue to attach them to the plywood 1/3 of the way in from each end, in between and square with the long pieces of 1x4. You should also pre-drill and use wood screws to attach the 1x4's to the 1x3's for added stability. Finally, cut lengths of 1x1 equal to the width of your 1x3 (it's probably 2.5 inches, but measure to get a perfect match). Glue them, standing on end, to the corners of the plywood and to the 1x4 framing. The train table will rest on these pieces of 1x1, along with the 1x3 borders of the sandbox. When the glue is dry, put the train board in place to make sure it fits properly. If it wobbles, sand down any high areas until the board sits correctly.
Finally, attach the plywood to the top of your old coffee table using generous amounts of carpenter's glue, and, for extra security, put a screw through the plywood into each corner of the coffee table. Make sure the plywood is properly centered on top of the coffee table.
Finally prime and paint the play table as desired. Be sure to prime the plywood as well because your kids will likely want to water down the sand at times, so you want the plywood sealed. Most tables easily accommodate a 50 pound bag of playground sand. And the openings in each end of the table's frame allow storage of sand toys at one end and train toys at the other.