There are many types of extendable table with various designs for pulling, lifting and leaf from round to square and many others. Build your own extension table can be as complex as you want or need to process. Can be constructed using minimal tools and offers good performance to your time investment. Cut four equal pieces of hardwood for your legs, and give the style you want with a router.
Curt four database tables 0.3 m that are three quarters the length and width of the top of the extendable table you are building and the four legs attached at appropriate angles to these rules. What you will look like a table with a hole in the center. Cut the top of your table full width you want to have.
Center it on the legs and the base assembly, and then measure each side carefully to make sure the base and legs are directly in the center of the lid large extendable table. Brand 0.3175 inches in length and width of the table top on each side and cut this section with a table saw. Make the longest first and then the shorter sections, not cut any corner piece.