Part of a series that begins with Blocking Notes (Intro).
The first decision about blocking (after deciding what it is you're blocking, of course) is what you want to block on. If you don't want to stretch the article you're blocking, you can get away with gently easing it into shape using your hands, in which case you can block on any clean surface. Counter-tops, towels, specialized blocking boards, foam mats, foam insulation, homosote boards, corkboard, mattresses, clean carpets, drying racks – anything flat and big enough to hold the article will do. If the surface might absorb the water, or be damaged by it, or it might not be clean enough, then putting a lint-free towel or other cloth on top before laying the knitted article on it is a good idea.
If you want to stretch or shape the article a little more than you can do with your hands, then you need to choose a surface that you can pin the article to. Use rust-free (stainless steel) pins or t-pins; others tend to leave marks on the article that are hard to get out. T-pins are a little stronger and are good for heavier articles or if you need to stretch the article a lot.
If you're blocking garment pieces, it's handy to have a schematic of the size and shape you want the pieces to be, and a tape measure to check the measurements.
Shetland and fair isle sweaters knit in the round are often blocked on a wooly (sometimes spelled woolly) or stretching board (e.g., at Camilla Valley Farm's Wooly Board), which stretches the body and arms of the sweater into the right shape. The only problem with this method is that the ribbing at wrist and hip tends to be stretched too much, so has to be brought back into shape afterwards, which you can do either by steaming the ribbing until it relaxes with a steam iron or over a boiling kettle, or wetting it and patting it into shape. [FEIT, p. 70]
If you're blocking lace or articles with long straight edges using pins, it's hard to get the edges really straight. This is where blocking or dressing wires are useful. These are long, thin, clean stainless steel wires that you thread through the edges of the articles. Then you pin the wires at intervals to the backing surface, which makes the edges straight and can help avoid little triangles showing up as sometimes happens when you just use pins. A variation on this is to use strong thread (e.g., crochet cotton in bedspread size, or buttonhole sewing thread), thread it through the edges, and then tie it to strong pins. When you pull the thread taut, it will straighten the edges.
Those who block a lot of lace often recommend lace blocking frames. The basic principle is to build a frame that looks like a picture frame, and then use a strong cotton thread or string to tie the lace article onto the frame. By adjusting the thread tension and angle, you can adapt the frame to any shape of knitted article, so it's good for shapes that are difficult to block properly using other means. Examples of blocking frames are at Knitpicks and Spannmax.