One cannot crochet without the hook. I know “Thank you Captain Obvious”. Its funny though, I have spent decades crocheting and never gave too much thought to the hook. My main concerns were the hook size and how it felt in my hand. I have recently learned, however, that there is more to a crochet hook than that.
There are five main parts to a crochet hook. There is the point, the shaft, the thumb rest and the handle.
The POINT is the part that goes into the stitches. It has to be sharp enough to go through the stitches, but blunt enough it does not stab your fingers or split the yarn.
The THROAT is the part that does the actual hooking of yarn and pulls it through the stitch. It has to be large enough for the yarn you are using but small enough to prevent the loop from sliding off. There are two types of throats on hooks, inline and tapered.
The SHAFT holds loops you are working with and its diameter is what determines the size of of your stitches. That is where the size ( called a hook gauge)comes in. in the US a size B has a 2.25 mm diameter and a much smaller stitch size than a US G which is 4mm.
The THUMB REST lets you rotate the hook as you stitch. It should be held between your thumb and middle finger in order to achieve the rotation.
And last, but not least, the HANDLE is used for balance.
Crochet hooks can be made from many materials. The most common are aluminum and plastic. The other materials commonly used are steel, bamboo, wood, or glass. I have never seen a glass crochet hook, but I have seen the others. What the hook is made from is important in that the type of yarn can make a difference. For example, silk bamboo can easily slide off of glass or plastic crochet hooks. In that case, a wooden or bamboo hook is rougher and might be a better choice. For most of my projects ( like the Horsies) using standard 4 ply acrylic yarn, I use an aluminum hook and for most of my cotton crochet pieces (like the Mishap Bears) I use a steel hook.
This is just a quick overview. There is so much more that goes into such a simple tool. There are quite a few ways to make your own hooks. Polymer clay, turning your own wooden hooks among others. I will stick to the use of them and not the making. If you are inclined to make your own YouTube has several.
“List of United States Standard Crochet Hook and Knitting Needle Sizes.” Wikipedia, Wikimedia Foundation, 3 July 2018, en.wikipedia.org/wiki/List_of_United_States_standard_crochet_hook_and_knitting_needle_sizes.
Vercillo, Kathryn. “Crochet Basics: How to Choose the Best Crochet Hooks.” Craftsy, 1 Dec. 2017, www.craftsy.com/crocheting/article/the-best-crochet-hooks/.
Brittain, Susan, and Karen Manthy. “Anatomy of a Crochet Hook.” Dummies, 2018, www.dummies.com/crafts/crocheting/crochet-hooks/anatomy-of-a-crochet-hook/.