Not to be too obvious, but if you cannot measure accurately, you cannot be skilled at woodworking. And to measure accurately, you need the correct measuring tools that do what you need. Length, width, height, depth, square, 45°, other angles, outer diameter, inner diameter, circumference, radius, center, level, and other measurements take different tools depending on the measurement itself, the material or piece being measured, or the tool for cutting or otherwise. Some of these are rulers, squares of various kinds, calipers, levels, angle-finders, moisture meters, and others I cannot think of or don’t know. I do know the ones I own and the ones I use on a regular basis. Some I use all the time and wouldn’t want to be without. Here are several:
My Starrett 4” double square is one of my most used tools period. I’ve had it for five or six years now and use it for virtually every project. It is small but mighty. The ruler has 1/8th , 1/16th, 1/32nd, and 1/64th scales. The thick base is absolutely square to the ruler and quite a bit thicker. I use it to check square when hand jointing an edge, to check width when hand or machine planing a board, to set blade height on the table saw and router, to monitor depth for a mortise, to check flat, straight and square for chisel and plane blades. I use it as a marking gauge with a pencil. And of course, I just measure with it for items 4” or less (3″ with the base). I love the way it looks and feels and works. I’ve got other measuring tools that can do some of what this one does, but this one is my favorite.
Speaking of Starrett, I have two other Starrett tools, a 12” combination square, and an analog caliper. I don’t use the combination square on a regular basis, but when I need absolute accuracy, it is there. I picked it up at a yard sale years ago, so I have no idea how old it is, and there is some wear on the scales. But accuracy is spot on and I trust it over my other combination squares. Besides its normal functions, it works especially well for checking flat on relatively small boards when hand flattening with a plane.
The Starrett caliper is a recent acquisition. I used a 6” digital caliper for years, and while it was very serviceable and accurate, I never liked being dependent on the battery, nor the fact that everything was in decimals. Having to look up the fractional equivalent was something I have always detested. So when I discovered the Starrett fractional dial caliper, I knew I wanted it. It’s not cheap (currently $111 on Amazon), so I had to wait. The moment it did arrive, I was in love. Not only is it dead accurate, but I know the exact fraction for the measurement, and that saves frustration and time. The moving mechanism uses a fine gear that moves along the fine teeth of the rail for a super smooth and solid feel. Now I can figure out immediately what drill bit I need for a pilot hole without conversions or looking at a drill chart. Need decimals? Not a problem; it has a decimal scale too—something I used recently to measure for drawer pulls. And I never have to change the battery. And it is super easy to recalibrate. Of course the caliper overlaps the 4” double square for OD (like tenons and screws) and ID (like mortises) applications, as well as for saw blade and router bit height, thickness gauging, and depth. In my recent office sideboard project, I used it to adjust the spacing between drawers and doors. The caliper gauge is easier to see and fits in much tighter spaces, but the square is more beefy. Sometimes I use the one I see first.
Of course, I have other oft-used devices: large and small rafter squares, a 3” Delve square, an Empire 8” tri-square, an 18”x12” carpenter square, an odd-job with 6” and 12” rulers, a ruled marking gauge, several combination squares, a Lufkin folding wood rule, several different measuring tapes, a bevel gauge, and a variety of levels. They are all good and needed for various applications. Of all these, I guess I like the Lufkin rule the best because I inherited it from my granddad. Interestingly, I have a nice set of Incra rules and they are useful when I need them, but they are not the go-tos that I thought they would be when I purchased them.
Measuring tools are necessary, and it is nice to enjoy using them. At this point, I don’t know that I “need” any others, though it is very easy to convince myself otherwise.