When we cut with the jigsaw by hand we usually find the unpleasant "surprise" (after using it for a while it is no longer so much a surprise, but we already know what to expect) from making cuts that are far from being precise cuts vertical and straight. The upper line of the cut, the one that we see and that we guide the saw, will seem perfect, but underneath the cutting blade is twisted following the softer areas of the wood. That is why if we think about mounting the jigsaw on a table, sometimes we discard the idea because we believe that the same will happen to us with the cuts we make. But with this simple guide for the jigsaw we can make perfect vertical cuts.
Al mount the jigsaw on a board We already saw how 14mm, when the cutting blade was well adjusted in the groove of the board, it remained quite vertical during the cuts. But still a system that keeps the jigsaw blade vertically and always at 90 degrees will allow us to cut the wood without so many concerns about the quality of the cut. Although whatever the system, it must be borne in mind that by adding the blade guide system plus the thickness of the board, we will be greatly reducing the cutting height that we can perform with our jigsaw.
This system that I use as a jigsaw guide may not be very pretty, but it is easy to make and to assemble and disassemble from the tabletop. The most difficult thing may be finding the necessary bearings and a long cutting blade of sufficient length. I use some bearings that I took from some simple children's skates. They have the advantage that they are small and do not reduce the cutting length of my saw too much. And to be able to screw the bearings, I simply put a nylon plug in them, which I then cut with the chisel.
With the nylon plug the screw is off-center, but this allows me to slightly adjust the position of the bearing relative to the jigsaw blade. Even so, and as I comment in the video, it would have been better to put only one screw at the beginning holding the upper plywood strip, to adjust the verticality of the sheet more easily, and once we were happy with its position we could screw it in definitively.
Keep in mind that it is still a DIY saw, so you cannot be asked for too much work or have the ability to cut a band saw or circular saw.
And more than anything in case you are curious, here I leave the measurements of my support. Mainly you have to pay attention to the fact that the bearings must remain in contact with the blade in its lowest position. The bearings are 23mm in diameter. Larger ones could be used, but would further reduce the cutting height.