Table slides are used to open and close a table to add a leaf.
This handy table accessory has been around since 1889 when Watertown Table Slide Company began in Wisconsin. It incorporated two years later and is one of the largest and premier manufacturers of table slides in the United States today.

Watertown uses only hard wood such as Birch and Maple for their wooden slides. The company uses a special treatment on the wood that sets it apart from all other slides.
According to the company, approximately one million board feet of lumber is used each year at the company’s Watertown, Wisconsin plant.
TYPES OF TABLE SLIDES
There are two basic types of table slides used for different style tables.
The Standard Table Slide is used on four leg tables and consists of a series of parallel wooden slats that slide back and forth on a guide block for extending the length of a table for adding a table leaf.
The quantity of sections and the length of each section determine how far the table will extend. This style slide is the very rugged and can handle heavy weight loads. A disadvantage is it is bulky and usually requires two people – one at each end – to open and close the table. >
Single pedestal tables require an Equalizer Table Slide to prevent sagging of the table when opening the table. This style features a rack and pinion gear or a pulley system that balances the table when opening and closing the table. The slides are designed to rise on the ends to keep it level when open. While generally smoother sliding action than wooden slides, these slides have limited extension capability.
HOW TO MEASURE
Table slides are sold in various lengths and it is important that you use the proper length table slide when choosing a new slide. To determine the appropriate length of the table slide for your particular table, measure the length of the table when it is fully closed without any leaves in place. The table slide should be no shorter than half the length of the table when it is fully closed.

Instructions for installing mounts of each type are given in the following links. Instructions for installing slides on a single-leg table. Instructions for installing slides on a 4-leg table.