I made this toe jack from stock steel I had laying around my shop. The Jack is an old Harbor Freight 6 ton hydraulic version. The base, sliding vertical and larger vertical plate are 1/2" thick, as are the braces.
I got the idea for this from some images I found on the net, but I added a vertical strengthening web on the top horizontal bar running from the larger vertical plate to the top of the jack, since I think that will likely see the most stress. This meant that I had to mill out a 5/8" wide slot for that web to slide in, at the top of the larger 1/2" plate. I surface ground all sliding vertical components to minimize galling. After all welding and assembly, I applied high pressure lube to these and it slides very smooth.
I will probably never try to lift more than 2 tons with this, and then not more than about 4"high, if that. I made up a cad drawing to make sure everything would fit together.