Bar Tack
A dense cluster of closely spaced stitches used to reinforce high-stress points in a sewn item, such as strap attachments, pocket openings, and zipper ends. Bar tacks can withstand hundreds of pounds of pulling force.
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Seam Allowance
The area between the stitching line and the raw edge of the fabric. Standard seam allowances range from a quarter inch for patchwork to five-eighths of an inch for garments. Consistent seam allowances are critical for pieces that fit together properly.
Selvage
The tightly woven finished edge that runs along both sides of a bolt of fabric, parallel to the warp threads. Selvage edges don't fray and are used as reference points for finding the grain line.
Grain Line
The direction of threads in a woven fabric. The lengthwise grain runs parallel to the selvage and has the least stretch. The crosswise grain runs perpendicular. The bias grain runs diagonally and has the most stretch.
Warp and Weft
The two sets of threads that form a woven fabric. Warp threads run lengthwise on the loom and are held under tension. Weft threads are woven horizontally across the warp. Together they create the fabric's structure and strength.
Right Side / Wrong Side
The right side of fabric is the front, intended to be visible in the finished piece. The wrong side is the back. Most sewing is done with right sides facing together so seams end up hidden on the inside.
Fat Quarter
A pre-cut piece of fabric measuring approximately 18 by 22 inches, created by cutting a half yard of fabric in half across its width. Fat quarters are popular with quilters and patchwork makers because their squarish shape yields more usable pieces than a standard quarter yard.