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Gathering turns the edge of a piece of fabric into a bunch of small folds that are held together by a thread close to the edge. Gathering makes the fabric shorter where it is stitched. The whole of the fabric pops into irregular, rolling folds beyond the gathered stitching. Gathering can be done by hand, with a machine, automatically, with elastic, or through channels.
Pleating and 
File:Pleats with seam.jpg, Pleated fabric
File:The New Dressmaker, 1921, Ill. No. 0326.png, An illustration of shirred fabric
Gathering turns the edge of a piece of fabric into a bunch of small folds that are held together by a thread close to the edge. Gathering makes the fabric shorter where it is stitched. The whole of the fabric pops into irregular, rolling folds beyond the gathered stitching. Gathering can be done by hand, with a machine, automatically, with elastic, or through channels.
Pleating and shirring
Shirring is a decorative sewing technique that involves stitching together many rows of gathered fabrics. Shirring reduces the size of the original fabric while adding texture to the resulting decorative fabric.
In sewing, shirring is two or more ...
are two different types of gather sewing.
In simple gathering, parallel
Parallel is a geometric term of location which may refer to:
Computing
* Parallel algorithm
* Parallel computing
* Parallel metaheuristic
* Parallel (software), a UNIX utility for running programs in parallel
* Parallel Sysplex, a cluster of ...
rows of running stitch
The straight or running stitch is the basic stitch in hand-sewing and embroidery, on which all other forms of sewing are based. The stitch is worked by passing the needle in and out of the fabric at a regular distance. All other stitches are ...
es are sewn along one edge of the fabric to be gathered. The stitching threads are then pulled or "drawn up" so that the fabric forms small folds along the threads.
Gathering seams once involved tedious hand sewing of basting, which was time-consuming, especially with heavy fabric. However, finer gathers could be achieved. Now, a quick and easy way to make a gather is to use a wide zigzag stitch
A zigzag stitch is variant geometry of the lockstitch. It is a back-and-forth stitch used where a straight stitch will not suffice, such as in reinforcing buttonholes, in stitching stretchable fabrics, and in temporarily joining two work pieces ed ...
with a sewing machine. Both the upper and lower thread are pulled long and placed in front of the sewing machine. Then zigzagging is carefully sewed over top of the two threads without catching the threads as it is sewn. At the end the thread is pulled and is then gathered.
Types
*Pleating or plaiting is a type of gathering in which the folds are usually larger, made by hand and pinned in place, rather than drawn up on threads, but very small pleats are often identical to evenly spaced gathers. Pleating is mainly used to make skirts, but can have other uses.(See main article Pleat.) *Shirring or gauging is a decorative technique in which a panel of fabric is gathered with many rows of stitching across its entire length and then attached to a foundation or lining to hold the gathers in place. It is very commonly used to make larger pieces of clothing with some shape to them.Caulfield and Saward, ''The Dictionary of Needlework'', p. 220References