These are usually filed so that the teeth are a cross-cut pattern, and they get used for much more than cutting tenons.
I find them indispensable in box making and carcass work as well.
Here are two of my favourite old tenon saws. At the top is a Colver Brosler 14 inch 12 PPI, and below it a Taylor Brothers 14 inch 11 PPI.
The handles are works of art, and fit the hand beautifully - decades of being handled have smoothed these, and added the patina that sweat and workshop dust combined to form in use. The blades are better than they look - there is dried tea-oil across them as a rust deterrent, and it looks a little patchy in pictures.
Of course tenon saws are initially designed for cutting tenons, but they are even more versatile than just that.
Sometimes they come in canted blade versions like this smaller 12 inch Taylor Brothers brass backed saw. This one has 12PPI. The canted blade allows me easier sighting to the end of the cut, and is especially useful when cutting dados.
I'll include a picture of my much more recent Spear and Jackson cutting dados - I haven't one handy using the Taylor.
Tenon saws are the workhorses of the woodshop, and I find it useful to have more than one. The most common sizes that I use the most, have 11 or 12 PPI.
Less commonly used - by me, at any rate - is a dovetail saw. I don't cut a lot of dovetails, and if there are a lot to do, I will use a router and a jig to save time. However, small projects like boxes, small cabinets and trays etc warrant hand cutting, as the dovetails can be finished by the time the jig is set up and tested.
This lovely example was made by Ian Wilkie and has a walnut handle. Ian has written a wonderful article on backsaws in this month's - issue 78 - Australian Wood Review.
It is a 10 inch saw with 15 PPI and a fine kerf, and being a dovetail saw, is filed rip - for cutting along the grain. Ian's work is stunning.
It is also useful for fine work and doubles as a crosscut saw in a pinch.
The standard go-to handsaw for panel work in my workshop is a 10 PPI Disston. The blade on mine has some spotting, but it is well away from the cutting edge. In spite of its looks this is a sweet little saw, and a joy to use.
In the past, when long dados were to be cut, I have used the 10 point panel saw, as I had nothing else. Recently I found a Spear and Jackson 10 point large tenon saw - for the odd occasion that large dados present. It has an 18 inch blade, and is so much easier to use and keep straight in the cut, than was the panel saw in this case. The number of times I cut long housings is infrequent, so this saw will outlast me and my grandchildren I expect. It has certainly seen little use over its life.
Not, technically a backsaw - (of course not - DOH!), but so useful none-the-less, is a little flush cut saw. I use this a lot in repairs to furniture, and it is superb at trimming broken dowels and fractured tenons. These are made with one flat side on the blade and a set on the teeth of the other. It leaves a smooth surface on the face of the timber, and cuts off the offending projection, flush with the surface.
The blade is flexible so that the handle can clear the surface when cutting.
Finally, I should mention a long backsaw, for cross cutting mitres and other angles. These are used in a mitre box, and are much safer for cutting short pieces than using an electric dropsaw or SCMS.
This saw is long at 24 inches, and is an 11 PPI saw for general work. Even though it is a long back saw, it uses a lot of its length just staying in the mitre box, leaving not too much to do the cutting. An even longer saw would be ever more useful here in my opinion.
This one is a Warranted Superior - probably by Disston.
For fine work, a smaller saw - around 15 PPI - and a wooden mitre jig are more useful.
Backsaws are real joinery workhorses, and a necessity for fine work. The fact that they are a pleasure to use is an added bonus.
Happy shavings to all .........................