Every quilter needs one block that cannot fail.
The one you reach for when a baby arrives in three weeks. The one you put in front of a beginner sitting at your machine for the first time, because you want them to win.
The rail fence quilt block is that block, and you will also see it called the fence post block. A handful of strips sewn along their long edges into a square, and the whole design comes from nothing more than turning the blocks as you lay them out.
What a rail fence quilt block is
A rail fence block is a set of strips, all the same width, sewn side by side into a square. That is the entire block. Three rails or four are the usual choices, and whichever you pick, the rails have to add up to a square.
There are no triangles, no bias edges, no seams that have to meet at a point. What the block asks for instead is consistency. If the rails finish at the same width, the block finishes square, and if the blocks finish square, everything you build from them behaves.
That is why it turns up in beginner classes and then keeps turning up in the work of people who have been quilting for thirty years.
Where the cutting sizes come from
You do not need a chart for this. You need one division and one addition.
Divide the finished block by the number of rails. That is the finished width of one rail. Add half an inch for the seam allowances, a quarter on each side, and you have the width to cut your strips.
The second number falls out of the first. Sew the strips together and the strip set measures the finished block plus half an inch across, every time, because the seam allowances you added at the two outside edges are the only ones that survive. So you crosscut the set at the finished block size plus half an inch, and each segment is a finished unit ready to sew.
One thing to watch. Divide the block by the rails and you want a number a rotary ruler can find: whole inches, halves, quarters or eighths. Five rails in a 7 inch block gives you 1.4 inches a rail, and nothing good comes of that.
Cutting instructions for the usual sizes
| Rails | Finished block | Cut the strips | Crosscut the set at |
|---|---|---|---|
| 3 | 6 in | 2 1/2 in | 6 1/2 in |
| 3 | 9 in | 3 1/2 in | 9 1/2 in |
| 3 | 12 in | 4 1/2 in | 12 1/2 in |
| 4 | 6 in | 2 in | 6 1/2 in |
| 4 | 8 in | 2 1/2 in | 8 1/2 in |
| 4 | 10 in | 3 in | 10 1/2 in |
| 4 | 12 in | 3 1/2 in | 12 1/2 in |
Look at the two rows that ask for 2 1/2 inch strips. Three rails give a 6 inch block and four rails give an 8 inch one, and 2 1/2 inches is exactly the width a jelly roll arrives in. That is why a rail fence quilt pattern is the classic first use for a strip roll. The cutting is already done.
Making the block from a strip set
Nobody sews these one block at a time.
Cut your strips at the width from the table. The full width of the fabric works. If you would rather not waste any, cut them to the unfinished block size times the number of units you need, plus half an inch to an inch for squaring up the end.
Sew the strips along their long edges into a strip set, using a scant quarter inch. A fraction of an inch lost on each of three seams is a block that will not make its size.
Then crosscut the set into squares. Measure the crosscut from a seam line rather than from the raw edge, so each unit is square to its own seams rather than to an edge that may have drifted.
Pressing the strip set
Set each seam first, then press the allowance towards the darker fabric.
Towards the dark, and the reason is shadowing rather than nesting. A dark seam allowance lying behind a light rail shows through from the front, and it is the kind of thing you only see once the quilt is finished and it is too late.
Nesting matters less in this block than in almost any other, and it is worth understanding why before you worry about it. Turn the blocks as you set them and the seams inside one block meet the plain edge of its neighbour, so there is nothing to lock against. The only joins that need matching are where block meets block.
Press as you go rather than sewing the whole set and pressing at the end. Strip sets bow as they are handled, and reaching into a finished set with the iron is what puts the bow there.
The design is in the turning
Because every block is identical, all of the design comes from which way you turn them.
All the blocks one way gives stripes across the quilt. Turning them in two by two groups gives a weave at a larger scale, which suits a bigger block.
The basket weave setting
Turning every other block a quarter turn is the setting with a name of its own. That is the basket weave quilt pattern, and it is what most people picture when they picture a rail fence quilt.
The rails appear to pass over and under each other, the way strips of wood are woven into a fence, and the illusion is entirely in the turning. Nothing is woven and nothing is appliqued. It is the same block, laid down facing a different way.
A basket weave quilt block reads best when the rails inside it run light to dark rather than light, dark, light. The eye follows the dark rail from one block into the next, which is what makes the weave look continuous instead of stripy.
Colour changes all three settings, in fact. Run the rails from light to dark and the same arrangements produce something else entirely, because the eye follows the rail rather than the block. Lay your units out on the floor and photograph them before you sew a single seam.
Take the whole thing with you
Everything on this page, including the size table and the three settings, is in a four page PDF you can print and keep beside the machine.
Download the rail fence quilt block guide. It is free, there is nothing to sign up for, and you may print it as many times as you like.
A free rail fence quilt pattern to use it in
If you would rather follow a whole quilt than design one, Railings is a free rail fence quilt pattern from Robert Kaufman, designed by Ariga Wilson. Four rails to the block, 56 by 72 inches finished, and fat quarter friendly.
Three more free quilt patterns in our library are built from strips and straight seams in the same way: Cross Hatch, Passage, and the Stacked Strips Runner if you want to try the sewing at table runner size first.
Questions about the rail fence quilt block
What size strips for a rail fence quilt? Divide the finished block by the number of rails, then add half an inch. A 6 inch block with three rails wants 2 1/2 inch strips. An 8 inch block with four rails wants the same.
How many rails should a block have? Three or four is usual. More rails make a busier block and more seams to keep straight. Fewer make a bolder one. The arithmetic does not care, as long as the division lands on a measurement your ruler can find.
Is the rail fence quilt block easy? It is the easiest pieced block there is. Straight seams, no matching, no bias. The only skill it tests is cutting and sewing the same measurement over and over.
What is the difference between a rail fence and a basket weave? None, in the block. The basket weave is a rail fence with every other block turned a quarter turn. Same cutting, same sewing, different layout.
Can I use a jelly roll? Yes, and it is the obvious use for one. The strips arrive at 2 1/2 inches, which gives a 6 inch block from three rails or an 8 inch block from four.
One set, then another
Sew one strip set. Crosscut it. Lay the units on the floor and turn them until something happens.
That is the whole appeal of this block. The sewing is over in an afternoon and the deciding is where the quilt actually gets made.
Marbelia Fernandes
The Fabric Hut Co-Founder
P.S. Cut one extra strip set. Not because you will need it, but because the moment you lay the units out you will want to try a second arrangement, and it is much easier to try one when you have blocks to spare.
