Introduction: Car Roof Rack Cross Bars

About: My wife and I love making things with wood. We build a musical instrument called a Kalimba or Thumb Piano and Wooden Barn Stars, Barn Quilts and old Rustic Signs.

This instructables is for people who have cars with roof side rails already installed and are looking to make a set of removable or portable cross bars for the occasions they are needed.

We are building a set of clamp-on crossbars.

My car has a factory installed set of roof side rails. I occasionally need to transport lumber from the lumber yard to my home so I needed a set of cross bars attached to the rails to make that work. I looked into buying a set from the dealer.... Whoa!.... are you kidding me? Even sets sold by third party vendors were high.

So.... I built a set myself out of some 1x4 lumber and a few pieces of hardware and they have worked out great and... without compromising safety at all, ... you can make them for less than 20 dollars.

After building and using the set I have, I thought of a few improvements and that's what I have drawn up here. I have included pictures of the units I built and you will notice some slight differences compared to the drawings.

Step 1: What You Will Need


  • Table saw
  • Drill
  • Sander
  • 1/2" drill bit


  • 1 - 8' x 1 x 4 board (I used Cherry because I had it on hand but cedar would be a good choice I think) This will be for the cross pieces. If you are doing this on a wider vehicle you might need more than 1, 8' board
  • 1 - 2" x 4" x 24" board this will make the 4 end pieces.
  • 4 - 3/8" Star Knobs
  • 4 - 3/8 x 4" carriage bolts
  • 4 - 3/8" fender washers
  • 4 - pieces of hardwood or plastic 1 1/2" x 1/2" x 6"

Step 2: Measure

You will need a couple of measurements before we get going...

  • Measure the distance between the rails at the front and rear positions (outside to outside) where the cross over will be positioned. You will cut your cross rails 4" longer than this measurement.
  • Measure the thickness of the rails. You will use this measurement when adapting this set to your vehicle.

Step 3: Cut List

  • 2 - 1" x 4" Length (Cedar would weather well and not need paint) Use your measurement PLUS 4 inches to cut the cross boards
  • 4 - 2" x 4" x 5 1/4"" wood blocks (shown green in the drawing)
  • 4 - Hard wood or plastic or PVC pieces (shown blue in the drawing)

Cut the parts above as shown in the drawings...

The green blocks have dadoes on top and bottom and a hole for the Carriage bolt. The top dado locks the cross board (tan) and the bottom dado locks the clamp piece. (blue)

The blue block....(I had a piece of 4" PVC pipe that I cut into strips on my table saw and used a heat gun to flatten them) You can use some nice oak or other hardwood to make these parts... just be sure it is made with something that will not split or fatigue over time!

Step 4: Putting It Together

The thickness of the green block between the upper and lower dadoes should be slightly less than the thickness of your cars rails. Make the dadoes deeper or shallower to achieve this. This will allow some clamping of the rail to occur when you tighten the star knobs.

The rails on my car are not parallel so be sure to measure before drilling the holes in the cross boards for the clamping pieces to get it right. It is likely, as was in my case, you could have a front and a rear crossbar.

Have fun! Think of all the tools you can buy with the money you save!

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