Yes, knit material can be altered. There are a few ways to do this, depending on the desired outcome. For example, if you want to make a garment smaller, you can take it in at the sides or shorten the length. If you want to make a garment larger, you can let out the sides or add length. You can also change the shape of a knit garment by adding or removing darts, pleats, or other shaping details.