A vacuum chuck for holding what? There are many variations possible.
I use a vacuum pump to hold work pieces on my bench while working on them. It's just some closed cell foam Weather stripping attached to a flat piece of wood in whatever shape that I need. I drill a hole part way through the wood from within the center of this Weather stripped area, and then a second hole from the edge of the board to intersect with this hole. I then install (usually epoxy) an air line fitting for the line that connects to the vacuum pump in this edge hole. This completes the assembly of my vacuum chuck.
In use, I attach this vacuum chuck to my workbench with a couple of screws. Then use some semi rigid air line to attach the vacuum chuck to the vacuum pump. Then I turn on the vacuum pump and then place my work piece down against the Weather stripping. As soon as there is a good seal, the work piece is pulled down tightly and is secure enough to rout, cut, shape, etc. Turning off the vacuum pump releases the work. The holding force is 14.7 pounds for every square inch of surface within contact with the weather stripping, if there are no leaks. I have a vacuum gauge on the vacuum pump that lets me see easily if there is a good seal and no leaks.
Rockler sells some vacuum chucks and a vacuum pump, but their prices are a bit high. I received some of their vacuum chucks as a gift and they work OK, but are a bit small. There are much better vacuum pump deals available than the one offered by Rockler. The refrigeration service vacuum pumps from Amazon are quite good. Get at least a 2.5 - 3.5 cfm pump for this. Bigger is always better. Add an inline air filter to keep sawdust out of the pump. The line that I use is 100 mm semi rigid plastic line. It comes in 100' coils and is quite reasonably priced, so unless the piece that I cut is long I never re-use it. The short pieces just go in the trash when the project is finished. The fittings that I use are designed for use with this tubing. 1/8" pipe on one end and 100 mm tubing on the other. The tubing just presses in and locks, but pressing the collar around the tubing releases it, so the tubing and fitting can easily be re-used. Make 90 deg cuts of the tubing ends with a sharp single edge razor blade and the fittings will not leak. Cut them at an angle or with dull knife and they will leak.
Charley