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Blocking, squaring, straightening - these terms are all synonymous to the technique of ensuring a fabric is properly prepared for fabrication. That is, the warp and weft lines are perpendicular to each other and a line cut following the weft thread is a straight line.

Symptoms of fabrics which were not properly straightened:

  • On a soft cornice, the fabric will have ripples running cross-ways through the flat section.
  • On straight hang panels, the lining will gap at the lower corner of the panel if either the panel and/or the lining have not been properly squared.
  • Swags, if not cut square or on a perfect bias will have a slightly lopsided look - even though the pleats are symmetrical from one side to the other.
  • Lining and face fabric do not mate perfectly along a wide valance piece. One fabric will pull the other out of alignment. Some severe cases will cause rippling on the face and not allow the valance to hang properly.
  • Vertical lines on valances or panels will not hang straight. They will pull slightly to one side or the other. In straight hang panels, a long vertical stripe will visually curl around and be impossible to dress in a straight line.

    Remember that these rules apply to lining as well as face fabric. If the face fabric is straight, but the lining is out of square, it will affect the finished treatment. Always square your lining.

Determining if a fabric is off-square:

It is important, before beginning a project, to know if or how much a fabric is off square. Cut the leading edge of the fabric on the grainline using the most precise technique for that fabric:

-- If a horizontal line is woven into the pattern, cut along that line.
-- Or, pull a weft thread and cut along the pull line.
-- Or, if absolutely impossible to pull a thread, draw a line following the printed pattern on the fabric.


Sometimes, you can visually see that a cut line is not straight. If the cut edge is curved (Illus 1), the fabric was pulled thru harder on each side than in the center. Usually the cut edge is slanted (Illus 2) because the fabric was pulled harder on one side than the other. If the skewing is not readily noticeable, fold the fabric length in half (Illus 3), aligning the corners and selvage edge on one side and let hang. If the bottom corners do not come together, the fabric is not square.

Squaring techniques.

There are three methods by which you can square the fabric:

1. One person:

Grasp the fabric and pull at intervals across the length the fabric. Fold the fabric in half lengthwise, matching the corners. If squared to within acceptable limits, you are finished. Otherwise, repeat the process.


For concave fabrics, pull to block following these arrows.


2. Two Person Team

For longer pieces of fabric, it is best to have a second person. The second person will act only as an anchor. They do not pull on the fabric, only provide the stability.

There are several reasons for using the second person as an anchor only: The puller has complete control as to how much pull is exerted on the fabric; Most fabrics don’t require the force of two people pulling; The amount of pull will be more evenly distributed; Finally, the anchor can be any kid or adult who happens to walk through the door - no special training required.

With two people, you will be pulling the fabric from the corners and along the edges, thereby aligning all threads at one time. The anchor and puller each grasp the fabric at diagonal corners (see the Two Person Team illustration). The anchor braces and will not release the corner during this process.

The puller pulls firmly. You will see and feel the threads realign themselves in the center of the fabric as you pull. Maintaining tension, use a hand-over-hand motion to work your way down the length of the fabric (the top of the illustration), grasping the fabric at 12-15" intervals along the selvage edge. Return to the corner using the same hand-over-hand motion and maintaining tension.

Continue to maintain tension on the fabric. Using the same hand-over-hand motion, work your way down the width of the fabric (the right side of the illustration) grasping the cut edge of the fabric. Return to the corner using the same technique and maintaining tension.

The reason for working the tension on the fabric along the length and width of the fabric is to straighten all the threads. Conventional teaching in home-ec had us pulling only on the diagonal corners. This worked to some degree, but only served to straighten the threads in the center of the fabric. Pulling along the edges pulls the threads into alignment throughout the cut piece.

Fold the fabric in half lengthwise and check the corners. If squared to within acceptable limits, you are finished. Otherwise, repeat the process.

3. Blocking on the table:

This technique requires a full-size workroom table. They are generally five feet wide by 8 or more feet long. They are padded and framed with ruled sides. To block a stubborn fabric using the table, lay it out flat on the table, aligning the selvage edges with the side of the table. Clamp or pin one end of the fabric to the table. You will have to pull the fabric so that the end of it is aligned with the end of the table. It is very important to clamp or pin the fabric closely to offset the tension you will be putting on it. If the fabric is a loose weave which might tear away or fray, turn the first 2" under and pin through both layers for increased stability.

At this point, if the fabric will tolerate liquid, you can spritz it down liberally with distilled water. The water relaxes the threads so it can be pulled. Take the other side of the fabric and pull firmly, aligning it to the other end of the table. Pin or clamp down securely. Steam the entire piece. Allow to dry, then unpin from the table.

This is probably the most effective treatment for straightening your fabric, but it does have a couple of downsides: You must have a professional workroom table. The fabric must tolerate steam and liquid. There is a possibility of uneven shrinkage due to the steam and water which is applied. Until the fabric dries, it will tie up your table for other projects.

Stubborn fabrics:

Many fabrics today are treated with finishes and heat which lock the threads in position and resist squaring. In some cases, you will have to exert quite a bit of tension on the fabric to pull it into alignment.

Cut away the selvage edge. Sometimes this edge will prevent the fabric from squaring up properly.

Some fabrics, if they can be treated with water, will respond very well to the squaring technique if thoroughly spritzed with distilled water. The water relaxes the threads, allowing them to be realigned.

Fabrics which have been treated with a rubberized backing (insulated and blackout linings, upholstery fabrics, etc) cannot be straightened. The backing prevents this. The upside here, though, is that they will hang square to their own selvage edges, regardless of the warp and weft lines. This is because the backing stabilizes the fabric. Do not try to cut on the straight of grain or block these fabrics. Simply square to your cutting table or us the T- or L-square to draw your cutting lines.

Finally, there are fabrics which will not square at all or within acceptable limits. If you suspect a fabric to be especially resistant to squaring, let it sit overnight to determine if it readjusts itself out of alignment. If so, it must be rejected

Acceptable Limits:

Depending on the job, there are various levels of acceptable limits:

Roman shades, soft cornices, any valance with flat, squared sections must use fabric which is squared to within one half of an inch. It is imperative they hang flat. Lining must square to same limits.

Long panels, swagged treatments, folded (jabots) treatments can work with fabrics which are squared to within two inches. The closer they are to square, the better they will work, but you do have some play here.

Unlined, unconstructed treatments, puddled panels, scarf swags, etc. can usually be fabricated without worrying about squaring.


Squaring fabric is becoming a lost art. Many new sewers are unaware of the importance of working with squared pieces. When combined with a practice of cutting as close to the straight of grain as the fabric and pattern will allow, you will ensure much easier fabrication, installation and dressing of your treatments.


If you enjoyed this article, you might enjoy:

Fearless Pattern Repeats - Part 1 - Basics of pattern matching and handling various types of repeats.

Fearless Pattern Repeats - Part 2 - all about stripes & plaids

Half-Drop & Drop Match Repeats

Cutting Techniques

Squaring Fabric

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