ADS48 The Original Aluminum Adjust-A-Square T-Squares Series
Product Review:
Adjust-A-Square
Big layouts made easy 
I bought my Adjust-A-Square (Johnson Level & Tool, Mequon, WI) over 10 years ago for laying out lettering and graphics on large signs. The adjustable 48-inch blade was great for those jobs. Making signs are a thing of my past but the Adjust-A-Square remains a useful tool in my woodworking shop.
Initial Impressions
One of the things I first liked about the Adjust-A-Square was that it is made from a heavy aluminum extrusion and features large, clear markings. The blade can be adjusted for angle and length, a feature that made the Adjust-A-Square more versatile. The more I used it in woodworking, the more I found to do with it.
The Basics
The 2"-wide and ¼"-thick blade is rigid and has remained straight over the years, insuring accurate layout or cut lines. Compared to many of the squares on the market, the Adjust-A-Square seems almost over-built but it was obviously intended to last a very long time.
A large, three-wing knob threads into the 22"-wide head piece (no nuts to lose), locks very well and has stayed that way for the decade-plus I have been using it. The blade fits into milled slots in the head at 90-degrees to insure repeatable accuracy. The clamping knob also locks the blade securely at any of the other marked angles as well as between them.
A milled slot in the arm allows adjusting the length from the full 48" down to 24". This comes in handy when working in confined areas, a situation I have encountered more frequently than I anticipated in woodworking. 
The Adjust-A-Square is given a clear anodized finish during manufacturing that has resisted tarnishing throughout my decade of use. The numerals and scale markings have also remained clear and easy to read. The blade has 1/16" graduations on one edge and 1/8" along the other edge.
In the Shop
The Adjust-A-Square has proven to be a great layout tool, particularly when working with sheet stock. Being able to draw a continuous layout line up to 4-feet-long makes those larger tasks easier and more accurate than trying to extend lines made by shorter tools.
The angle markings on the head are quite accurate but to be woodworking precise I use a protractor or angle finder to set the Adjust-A-Square or simply use an existing angle to set it when I need to replicate such a cut on a new piece.
The simple task of marking a 4 by 8-foot sheet of plywood for cutting can be a less than accurate chore when the layout tools do not reach all the way across. I have probably used as many "cheats" as anyone for this task but always go back to the Adjust-A-Square for its simplicity and accuracy.
Because the blade is 1/4"-thick, you don't even have to draw a layout line for many cuts made with a circular saw. Position the Adjust-A-Square for the cut, clamp it in place and use it as a guide for the saw. These types of cuts have never been faster or more accurate.
By the way, if you do any work around the house from repairs to remodeling, the Adjust-A-Square is great for marking and cutting drywall as well as most forms of sheet stock.
Conclusions
You might not use it every day but the Adjust-A-Square will be a welcome addition to your layout tool selection and if you are like me, you will be reaching for it more often than you may suspect. The full-width reach makes the Adjust-A-Square a natural for breaking down sheet goods and it is perfect for many layout tasks on those same materials.
The Adjust-A-Square from Johnson Level and Tool is not a budget-breaker either. Get one, hang it one the wall and remember where it is. You will be glad it is there before long.
