This technique is a classic, often used for adding names to Christmas stockings, for adding color in small sections of intarsia, and for “fixing” mistakes in other types of knits.
With yarn threaded on a tapestry or darning needle and the right side facing, follow the path of the knit stitches over and under, taking the needle to the back to move it up, down or sideways.
With duplicate stitch you can create designs on existing fabric, allowing you free rein to “draw” whatever shapes you wish. Since its building blocks are stitches, your shapes are somewhat constrained by their dimensions. For example, stockinette stitch stitches are usually wider than they are tall (e.g., five stitches but seven rows to the inch using worsted-weight yarn).
The free-form shape at bottom right of the yellow swatch is worked in yarn that contrasts with the background, but is approximately the same thickness, or weight. The single-stitch “dots” of color to its left are a multicolored ribbon. Below, on the pink swatch, a tiny pyramid of glitzy yarn wound with hues related to the background draw the eye.
Techniques include duplicate stitch, crochet and knit chains, couching and weaving. Elements include beads (spun on the pink yarn), buttons, stitch markers on jump rings, ribbon flowers, fringe trim from the notions counter.