You've had that adjustable work table in your family for a generation or two and it is beginning to feel its age. It may have been set at a particular height for decades and now you wish to adjust the height for a project, but the adjustments just will not work. The bench seems to be stuck at the height for which it's been existing.
Step 1 - Disassembly
Remove all items from the table prior to working and gather all applicable tools and materials. Turn the table upside down. Spray bolts with WD-40 and let it saturate into the parts for an hour or so. After that, the bolts and moving parts will be released from the corrosion that may be holding them tight in place. After an hour use a socket wrench, nut driver or wrenches of the appropriate size to release the bolts from the legs. Pull each leg from the table top assembly in a direct upward motion to eliminate the chance of jamming them by pulling at an angle.
Step 2 - Cleaning the Corrosion
After the legs are removed from the assembly spray with rust removal compound and use emery paper to sand down any flaws or corrosion that is on both parts of the legs. Clean off the surface as applicable in the directions on the container of rust removal compound. After the part is clean and dry, spray a thin layer of primer on both pieces to conceal all bare metal visible. Let dry as per the instructions and re-coat as instructed. Let the primer dry for 24 hours after the final coat. If the bolts and nuts are rusted, it is best to replace them. Just go to a home improvement store, if you do not know how to choose the correct replacement just ask an employee, they are more than happy to lend a hand.
Step 3 - Reassemble
Spread a thin layer of grease on the legs to allow lubrication in the future adjustments. Place the legs on to the primary structure and set all legs to the same height. Slide a bolt in through the hole on the structure and install the nut snug, not tight. If using new bolts and nuts thread the nut on to the bolt prior to installing. After installing the legs, turn the table on to its feet. If any of the legs are not set to the correct height make the adjustment. If the table is still rocking just use small wooden shims to slide under the legs to eliminate the movement.
Step 4 - Maintenance
To avoid future problems, adjust the legs slightly about every 3 months to prevent any future sticking on the legs. If necessary apply another thin layer of grease to help keep the legs lubricated. These few simple steps will keep your table working long and strong for any work you may need to do in the future.