What is Interlock?

Interlock fabric is a double-bed circular knit made by interlocking two 1x1 ribs. Both faces look flat, like the face of single jersey. With the same yarn it is thicker and more stable than single jersey, and its edges do not curl. It is used in T-shirts, baby clothing and close-fitting garments. Turkish suppliers call it interlok. Note that in the sewing industry “interlock” is also a machine name (see below).

Interlock fabric structure

The name comes from two 1x1 ribs “locking” into each other to form one fabric (CottonWorks). The wales on the two faces sit directly opposite each other and are locked together, so even when the fabric is stretched, the purl loops behind are not visible (Jamshaid et al., 2021). The result is a balanced, flat-lying structure: edges do not curl and, unlike single jersey, stitches do not run (Jamshaid et al., 2021; CottonWorks). Because the wales of one bed sit between those of the other, the tendency to narrow crosswise is half that of 1x1 rib, and stretch is low both crosswise and lengthwise (Gülsevin, 2005, cited in Dönmez, 2008).

Double-bed fabrics bond two fabrics during knitting, so they are heavier, more stable and curl less (CottonWorks). With the same yarn and stitch length, the three basic structures rank as follows (NPTEL):

How interlock is knitted

Interlock is knitted on circular machines with two needle beds, cylinder and dial, which in Turkish are also called “çift plakalı” (double plate) (Erkoç, 2006, cited in Dönmez, 2008). The needles are set opposite each other, but opposite needles do not knit at the same time; one visible course needs two feeds (CottonWorks). The first feed forms loops on odd-numbered needles and the second on even-numbered needles, so the second rib fills the gaps of the first (Dönmez, 2008). Because the structure is two ribs knitted into each other, a much finer yarn is chosen than if a single rib were being knitted (NPTEL, Module 5).

Types and variants

• By fiber: Interlock fabrics knitted from modal, viscose and polyester yarns have been studied alongside cotton (Jamshaid et al., 2021).
• Different yarn on each face: Feeding different yarns to the odd and even courses can give cotton on one face and another fiber on the other (NPTEL, Module 2).
• Elastane interlock: Full-elastane, half-elastane and elastane-free interlock fabrics exist (Ertekin, Oğlakçıoğlu and Marmaralı, 2018, cited in Cingü, 2022).

Penye and other names not to mix up

Penye is a Turkish yarn term for combed cotton, not a knit structure, although it is also used loosely as a fabric name (see Single Jersey). Interlock knitted from combed cotton yarn can be very soft (CottonWorks). Write structure and yarn separately: “interlock, Ne 30/1 combed cotton”.

• Interlock sewing machine: In the sewing industry “interlock” also appears as a machine name. For example, Pegasus presents its W3500P series, developed for sewing knitted garments, as a “flatbed interlock sewing machine” (Apparel Resources, 2014). That is a sewing machine name, not a fabric structure.
• Double jersey and double face: Dönmez (2008) uses “double jersey” for rib knit, and Cingü (2022) treats “double face” knit as a structure separate from interlock. Do not use these names as synonyms of interlock.

Interlock weight (GSM)

There is no standard weight range; weight varies with yarn count, machine gauge and stitch length. One raw knitted-fabric manufacturer gives 180–260 g/m² (5.3–7.7 oz/yd²) for interlock (Karcem, September 2026), and ranges differ by source. A measured example: samples in Ne 30/1 yarn, knitted on a 26-inch, 20-gauge interlock machine and wet-relaxed, weighed 245–271 g/m² (7.2–8.0 oz/yd²), and the all-cotton sample 260 g/m² (7.7 oz/yd²) (Jamshaid et al., 2021). Because interlock is knitted with finer yarn, do not compare single jersey and interlock by GSM alone. 1 oz/yd² ≈ 33.9 g/m².

Uses

Interlock is used in T-shirts, dresses and baby clothing, in pajamas and loungewear (Pratt Institute), and in close-fitting garments such as turtleneck tops (CottonWorks). Makers of pajamas and loungewear are listed in the Pajamas and Loungewear category.

What to check when sourcing interlock

1. Do not compare with single jersey by GSM alone: ask for yarn count, machine gauge and stitch length too.
2. Factor in cost: with the same yarn and stitch length, interlock contains more yarn per square meter than single jersey (NPTEL); it is also knitted with finer yarn, and finer yarn generally costs more (Cotton Incorporated, ISP 1009).
3. Check stretch: interlock stretches less than rib (NPTEL). For close-fitting products, ask for the elastane version and recovery values.
4. Compare samples for hot-climate products: in one study of cotton and polyester fabrics, interlock and 1x1 rib had higher thermal resistance, and single jersey higher water vapor permeability (Oğlakcıoğlu and Marmaralı, 2007). This is one study under specific conditions, not a general rule; test with your own yarn and weight.
5. Ask for the interlock shrinkage result: width and length change is measured to ISO 5077, and washing and drying follow ISO 6330 procedures.
6. If you need a more stretchy band, consider rib; if you need a lighter, thinner fabric, consider single jersey.