Blood, Sweat, and Sawdust

Going against the grain

Tag: sector

How to Use a Sector

The sector is an excellent tool for proportioning your furniture designs quickly and accurately.  Last week, I showed you how to make a sector from an old folding rule.  I also discussed how to use it.  Despite its simple nature, I thought this discussion could benefit from some visuals.

How to Use a Sector

Align the sector

1. Start by aligning the sector with the edges of the space you are dividing.  Since I am dividing the space into 4, equal segments, I align it with the number 8 mark.Align a divider with the sector

2. Next, without adjusting the sector, align a divider with the proper marks.  In this case, it is the number 2 mark.


3. Next,  walk off your divisions with the divider.


That’s it.  Four perfectly spaced divisions.  And, it only took a few seconds to complete.  No complicated math.  Simple.

If you have any questions, don’t hesitate to let me know in the comments.  Now, go out there and find yourself an old folding rule.



Make a Sector from an Old Folding Rule


The Sector

How do you quickly divide an interior space of 17 5/8 inches into three equal parts?  With a sector.  Furniture builders and architects have reached for the sector often to quickly divide spaces.  Unfortunately, it’s a tool that has been largely forgotten in today’s machine driven world.

The sector is nothing more than a pair of folding arms used to create a series of proportional triangles.  To divide a space, line up the sector with one of the markings that is a multiple of the division you want.  For example, if you want to divide the space into four equal parts, you could use the four, eight, twelve…you get the point.  Then, just set a pair of dividers to the division you want.  If you selected twelve, align your dividers with the three.  If this isn’t entirely clear, don’t worry.  I will write another post detailing their use.


To make the sector, start by marking the center point of your hinge, where the inside of each arm intersect.  I used an accurate straightedge to carry a line through with a pencil.  It’s critical that this is accurate.


Then, walk your increments off with a pair of dividers.  You may have to use some trial an error here.  Twelve increments works great, due to the amount of whole number ratios you can get.  Unfortunately, my first step would have still be in the brass, so I went with eight for this one.


With the increments stepped off, I carefully carried a line across both arms with a marking knife.

Completed Sector

From there, it was just a matter of filling in the lines for visibility and numbering my graduations.  Stay tuned for part two, where I will demonstrate the sector in use.

Click here for part 2 in this series: How to use a sector