What are you trying to block? When blocking lace items, I stretch it out and pin it, then mist it lightly and let dry. This also works if you are trying to block something with stockinette edges that curl. You can also block by laying the piece down and covering with a wet towel. Or you can block by ironing. It all depends on what the type of item. There are a lot of methods.
By double knitting, do you mean the technique of double knitting that creates a two-layer fabric?
yea i mean the two-layer fabric with two colors .. what happened was that the scarf that i'm making .. the yarn got all wrinklie in the ball .. so when it was unraveled the yarn is all wavy .. and i think it's making the scarf wavy .. so i thought that if i blocked it .. it'll go back into place?
If your yarn is not an acrylic, Hatsune, I might suggest you try the steam method of blocking. You would lay your piece down on the ironing board and place a thin dishcloth over it. Hold the iron over the cloth, just barely touching it and move it back and forth over the piece. The steam should relax the yarn. But this method is not recommended for acrylic yarn because it melts.