Witness Marks

I asked a question on MeWe the other day and received a response that mentioned witness marks. To be honest, this topic is something that I learned as a child, had reinforced in the Army, and now I do without thinking about it.

Witness marks are any kind of marking on two or more assembled parts that show their alignment. Used to show that the parts haven't moved, or how those parts were properly assembled, witness marks are a good way to save time and ensure that things stay together.

• A line scratched at the junction of two metal pieces is one common form. Using a scratch awl or pin punch to mark a nut/bolt or a joint between metal parts that aren't supposed to move will show you if those parts need to be snugged up. This is also handy when disassembling something intricate or precise, as it shows you where things have to go when you put it back together. I've also seen groups of dots lightly punched into sheet metal parts to mark which edges go together on panels that have been removed for maintenance.
• Using a permanent marker to draw a line on pipe joints to indicate proper alignment. When working with plumbing, especially in older houses, there are a lot of obstacles to route around. “Dry fitting” your pieces of pipe in place before soldering or gluing the joints saves frustration and time. Putting witness marks on those joints when they're in the right place makes final assembly much easier.
• A dab of nail polish or lacquer on a bolt/nut to show any motion in the nut from vibration or tampering. Working on missile components in the Army, we used a very rugged form of lacquer (named Glyptal) to seal and mark important bolts after assembly. It wasn't used as a form of Lock-Tite to prevent movement; rather, it was there as a security seal to warn that the assembly had been tampered with. Safety wire was used if we needed to make sure a nut stayed where we wanted it, but that's almost a lost art today.
• Larger assemblies often have the fasteners marked after they've been torqued. This is a quick visual check to make sure nothing got missed. Torqueing the 32 bolts that hold a 6' tall tire onto a piece of farm equipment can be a challenge, so we use a paint pen to mark each bolt as it is torqued in the proper pattern. It's also an easy way to check each morning to make sure none of them shook loose as the machine bounced through the fields the day before.
• Prefabricating small structures for final assembly elsewhere is a common prepper project. It may be an ice fishing hut, deer blind, or even something as mundane as a tent, and using witness marks on the parts makes things go together faster in the field. Older-style tents with metal pole frames can be a challenge the first couple of times you set them up or if it has been a while since you tried it. We color-code the metal pipe joints with different numbers of stripes to make sure they all get put together the same way every time. Colored electrical tape works and is easier to use on thin round pipe than paint, but that can add thickness to the pipe and make it harder to slide through loops and channels in the tent fabric.

Some of my examples may seem a little OCD, but when you're an hour away from the nearest hardware store or repair shop, you don't want to have things come apart on you. Security, safety, and peace of mind are all part of being a prepper, and using simple things like witness marks can help in all three.