Never knew there were so many contractors here. I am, too. Started in the trades in '72, and have had my own outfit for almost 40.
I have always work for or have been a general contractor. To me, I don't and won't use a fixed blade on the job site on a daily basis. First, there are so many good options for folders, I don't want to have a knife hanging off my belt of my tool bags (I still work on occasion with the guys). In my maintenance work, we work in occupied spaces and I don't want any commentary on someone carrying a knife. Second, more structured sites will not allow anything that could be construed as a weapon (remember a few years ago when hijackers used box cutters...) to be displayed. Third, as long as I have worked in construction I have never quit being amazed at how fast tools (especially an attractive one like a cool knife) grow legs. If I drop my tool bags and run to the lumberyard, I want my stuff to be in the bag when I get back, and I don't even want my knives borrowed.
Personally, I have never needed a fixed blade. With utility knives and sharp blades, recip saws, circular saws, oscillating saws, etc. all at my finger tips it is easy to only lightly mistreat a knife as heavy cutting chores are more easily handled by the correct tool.
I like the suggestions from the guys for good quality knives you can rely on that do a good job on site. The ZT350 is indeed a winner (and then some), and when I got my RAT1 I used it for nearly 3 years non stop since I was so happy with it. Plenty of handle, just the right amount of blade, and if desperate I can put a rough edge in it with a piece of wet-n-dry sandpaper. Despite all the variety of chores, and cleanup to remove caulk, tar, adhesives, etc. with charcoal lighter fluid, my ZT and RAT are still locking up tight.
Buy a knife that could get torn up (wait until you see what you will be doing with it) and then make a decision to get something better if you want. I still like a good, inexpensive knife in my rotation lineup ready for some real work, one that I won't get bent if something happens to it. Nothing beats that sickening feeling of tearing up that mirror finish, foil thin-razor edge when cutting cardboard and you hit a large, hidden staple. Your blade looks like Alfred E. Neuman's smile...
Robert