Well, when one is drawing, or drafting especially, it is useful, if not necessary, to have a ruler. And one might think that all rulers are the same. But they’re not. Some rulers have uneven edges, or mis-marked inches.
A cheap ruler might cost half a dollar, and a good one might cost a full dollar. It’s not much difference and definitely worth it. The Westcott rulers that I have here are very functional, durable, and standard. Then have straight edges and correctly marked inches. One is clear acrylic and the other is steel. I use the steel for inking and the clear for sketching. I would recommend two rulers for that reason. And these are flexible, and the markings are wear-resistant. My only real complaint would be that the acrylic ruler scratches a bit too easily.
This sounds much more like a recommendation than a review, and it is, sort of. It’s a no-brainer to get a ruler. Getting a good one is not much more expensive than a cheap one, and these work great, they’re some of the best I’ve used.