I will often make items on larger needles because of my arthritis. When you use larger needles, but do not want holes, you either have to use a thicker yarn, or work several strands together.
I wanted a full length knit coat. I wanted it to go with all the brown clothing I have. But the thought of all tan/brown just seemed boring. I found this tan yarn that had speckles of blues and greens, but working three strands of that had too much color.
Solution? Two strands of tan worked with one strand of the speckled tan.
I done this for several different coats to create visually interesting color patterns.
These are shorter versions of the same coat. My coat is two strands of grey and one strand of black worked together. My daughter's is two strands of light lavender worked with one strand of medium lavender.
It's a fun way to create an item that is unique to you!