Post Marking Jig

Ever tried to wrap a perfectly straight, level pencil line all the way around a 4x4 or 6x6 post using a standard speed square? It’s a total pain. You mark one face, slide the square to the next face, line it up by eye, and by the time you get to the opposite side of the post, your lines miss each other by a quarter of an inch.

If your marking lines don't line up, your fence brackets, deck joists, or pergola beams are going to go up crooked and create a non-zero chance of your project falling apart the very next day.

This 3D-printed saddle collar pack is a simple, no-nonsense DIY solution. It gives you a rock-solid, 3-sided physical straightedge that guarantees your pencil lines are perfectly square and perfectly continuous across three faces of the post in a single pass.

The Problem This Pack Solves

Instead of moving your square three different times and guessing if it's level, you just slide this U-shaped collar onto your lumber.

• Perfect 3-Face Alignment: Because the tool wraps around three sides of the post simultaneously, you can trace your pencil along the top edge to mark the front and both sides in one continuous motion. No slipping, no misaligned marks on opposite sides.

   

• Flawless Bracket & Leveling Setup: Once your line is marked perfectly square around the post, mounting Simpson Strong-Tie brackets, post bases, or rails at the exact same height becomes incredibly fast and accurate.

   

• True Structural Dimensions: Standard lumber isn't actually the size it says on the label. This pack includes dedicated files for both common post sizes, designed with a tiny bit of built-in clearance so they slide smoothly over rough, weathered, or slightly swollen job-site wood:

   

  • 4x4 Post Version: Tailored for true 3.5" x 3.5" dimensional lumber (perfect for standard fence runs).

     

  • 6x6 Post Version: Tailored for true 5.5" x 5.5" dimensional lumber (perfect for heavy-duty gate posts, deck corners, and backyard pergolas).

Print Settings & Recommendations

This is a functional shop tool, so it needs a little bit of extra strength to act as a reliable straightedge and handle being tossed into a tool bag.

• Material: PLA works great for quick weekend projects. If you plan to leave it out in the hot sun on a job site, PETG, ASA, or ABS is recommended so it doesn't warp in the heat. Better yet, use some stiff TPU for a little give.

   

• Orientation: Print it flat on its back (the "U" facing straight up) or standing vertically. No supports are needed!

   

• Wall Loops/Perimeters: Bump this up to 3 or 4 walls. You want the top guide edge to be nice and solid so your pencil doesn't wear down or deflect the plastic over time.

   

• Infill: 15% to 20% (Gyroid or Grid).