Production Carpentry Techniques:

Pre-Assembling Fence Sections
With A Jig

In This Article:

A simple fixture is made from OSB, lumber, and angle brackets. Eight foot sections of picket fence are assembled in minutes.

Related Articles:
Skill Level: 2 (Basic) Time Taken: 15 Minutes per 8 foot section

By , Editor


To build a dog kennel, we initially bought materials for 64 feet of fence. I've manually laid out many sections of fence before, but the thought of marking and squaring each picket (there were 96 of them) made me cringe. I could have made a simple wood spacer jig to give me the correct spacing between pickets, but that does not solve the problem of positioning the picket vertically. And small inaccuracies can get multiplied into large errors when using simple spacing jigs.

Having an engineering background, I knew that a simple fixture could be built to quickly and accurately lay out the boards for assembly. I spent about half an hour designing this fixture, and about 15 minutes building it.

The Fixture:

Assembly fixture used for building sections of picket fence.
The components:
A. 4x8 sheet of 5/8" thick OSB.
B. 8' 2x6, set against part "C" and attached to OSB with deck screws.
C. 8' 2x4, on edge, aligned with edge of OSB and attached with deck screws.
D. 2x4, approx. 45" long, aligned with 4' edge of OSB and attached with deck screws.
E. 8' 2x4 laid 42" away from inside edge of part "C".
F. Simpson Strong-Tie small steel corner brackets. Quantity used: 22. These were attached with Simpson Strong-Drive screws.

I estimate the cost of the fixture materials to be less than $25. Since everything was screwed together, all materials can be re-used.


Another view of the fixture.


The metal brackets were carefully laid out at 8.25" intervals. This spacing was determined by the width of the smallest dog that would occupy the fenced enclosure. The pickets were 1x6 treated pine, which have an actual width of 5.5". I figured that 2.5" to 3" open space between pickets would suffice to keep the little critter from escaping.

See Calculating Picket Spacing at the end of this page.


The Fence Rails:

The first step was simply setting two 8-foot treated 2x4's against their stop blocks.


Picketing The Place:

Then we set the pickets in place. The first picket rests against the end 2x4 stop block, and the other pickets rest against the metal brackets.



To attach the picket to the rails we drove in two deck screws at each end of the picket.


I adjusted the colors in this photo to better discern between the green treated lumber and the plain wood of the fixture. 

The last picket (working from left to right) was aligned with the end of the treated 2x4, so no metal stop was needed. This fact turned out to be a small problem (with the overall appearance) because I had hastily designed this fence project.


The completed section of fence. It took about 15 minutes to assemble each section.


The section simply lifted off the fixture, unless we happened to drive a screw into the fixture boards instead of the rails (which only happened once).

Continue to Installing The Fence.



Boring Technical Stuff:  

Calculating Picket Spacing:

I built sections of fence with pickets that aligned with both ends of the rails. My initial thought was to install the fence sections between the fence posts (so the posts would be fully visible from the front), but as I installed the fence my approach changed.

There are two basic cases in fence picket layout: 

1. Picket quantity exceeds number of spaces. To illustrate, look at your hand. You have five digits (hopefully) but there are only four spaces between the digits. My fence sections had 12 pickets and 11 spaces, which was not the best idea. But this approach is necessary sometimes, such as with garden gates.

2. Picket quantity equals number of spaces.

There are two cases within this situation:

  • Full space on one end
  • Half-space on each end. This is what I should have done.

Math Time:

Case 1: 

To determine the exact spacing of the pickets, I had to do a little math. There were some given quantities: The picket width (5.5") and the length of the fence rails (96"). I estimated a starting value for the spacing distance by measuring the width of the smallest dog, (not a simple task) which was just under 4 inches. So to be on the safe side, I chose 2.5" as the starting dimension.

Now I can do this math in my head. I saw that the picket plus the space equaled 8 inches, which meant 12 pickets and 12 spaces. Had I been thinking clearly, I would have simply chosen the 8 inch pattern and figured out how to divide up one of those spaces so half of it appeared at each end of the rails. But I chose the sub-optimal approach and proceeded to compute the exact spacing for only using eleven spaces. It looked like this: 

12(5.5) + 11S = 96  where S is the length of the space between pickets.

Solving this yielded:

66 + 11S = 96
11S = 96-66
11S = 30
S = 2.727 inches, which I rounded up to 2.75"

Thus, the length of the repeating pattern (i.e. from the start of one picket to the start of the next picket) was 5.5 + 2.75 or 8.25 inches. This worked great! Once installed, the pickets were perfectly uniform, square and parallel. The fence sections really looked professional. Until I installed them.

A general formula could be devised for fences like this:

PX + S(X-1) = L 

X = Number of pickets
P = Picket width
S = width of open Space
L = Length of fence rail

Of course, you can only have one of the four quantities unknown, that would normally be S, the open space amount.

Case 2:

Here you can just chose a spacing that, when added to the picket width, is divisible into the length of the rail.

(P+S)X = L

But for the preferred assembly technique (half a space at each end of the rails), the only complication arises in determining the starting point for the pattern of picket layout. And the starting point is simply a distance one-half of the open space width (S/2) from the end of the rail.



Continue to Installing The Fence.

Related Article: Cutting Fence Pickets



Tools Used:

  • Cordless Drill/Driver
  • Tape Measure
  • Framing Square

Materials Used:

  • Lumber, 2x4x8'
  • Fence Pickets, 1x6x4'
  • 2" Deck Screws


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Copyright © 2001, 2005

Written March 21, 2001
Revised January 12, 2005