Years ago when I first started getting interested in making sushi rolls, I could not figure out what the heck I was supposed to do with the bamboo mat. Various instructions made it sound like you rolled up the sushi and the bamboo mat like a jelly roll, and then unrolled them both, and then rolled just the sushi, which made no sense at all. Finally I just gave up and never used a mat.
A few days ago I was making sushi and thinking, "I really need an extra 20 fingers to keep the stuff in the roll while I roll the nori over the rice" and suddenly a vision of dozens of little bamboo pieces running lengthwise along the roll made sense. What the recipes neglected to mention (and what seems obvious to me now) is that you turn over the bamboo mat just once, until the nori completely encases the rice, and then unroll just the mat and continue rolling the sushi up in the nori (or not, depending on how much nori you're using per roll). With the constant, even pressure of the mat on the sushi, I now make really tight rolls. I also noticed that it's easier to spread the rice on the nori when it's on the mat, maybe because the nori isn't on a totally flat surface. So: if you have a bamboo mat, use it. I'm now in love with mine.
In other appropriate equipment news, after 2 patchy sunburns on my back last year I decided that boyfriends are not dependable sunblock applicators. Yesterday before my 20-mile bike ride I sunblocked my back using a rubber spatula. Perfect.