Wrist rollers are simple devices that provide effective forearm workouts. They are rods with weights attached by a short rope which you twist one way to raise the weight and the other to lower it. They're easy to make yourself - here's how to construct two different types of wrist roller: the conventional long skinny one, and a short fat one for a remove-the-lid style workout. Both can be had commercially for ~$20 or ~$45 (the "Forearm Blaster" and "Twist Yo Wrist") respectively if you're less enamored than I with building things.
Step 1: Materials
Our sofa broke, and as is usually the case when things break irretrievably, we (the kids & I) tore it down. We recovered a treasure trove of screws, springs, two caster wheels, lots of fabric and wood. The hardware was kept, the springs recycled, fabric ripped up for rags, and the wood sawed up for firewood. Well, nearly all of it. Some of the wood was OK and we like making stuff, so it got used for the wrist rollers. You probably don't want to sacrifice your sofa; the point is simply that any old scraps of wood are fine for this project.
This project is especially easy if you have access to a table saw and a router, but a hand saw and a plane would work fine too. Just more elbow grease involved.
Step 2: Laminate
Laminated wood is really strong. We glued two pieces of wood that were about 14" × 2" × 1" together, and made another 5-layered sandwich of 4" × 1" boards. Liberal amounts of wood glue and clamps were used and the sandwiches were left to dry for an hour or so.
You probably won't have a broken sofa handy, so just glue a couple of pieces of 2×4 together instead. A 2×2 is fine for the long skinny roller.
Step 3: Square
I am lucky enough to own a table saw so making the wood square was easy - run them through a few times to clean up all the sides and make the dimensions the same in both directions. You want one piece about 2" and the other about 4" square, but the exact values aren't critical.
Step 4: Octagonalize
This is one of my favorite operations on the table saw, because it is easy and effective. Angle the blade to 45 degrees, then lay the square on edge against the blade (so the square is a diamond). Bring the fence up to touch the edge. Remove, start the saw, and trim off all four corners. If you started with a square of edge length 1, you will have an octagon of edge length √2 - 1 (= 0.4142...). An octagon is of course not a circle, but it is close enough for our purposes.
Step 5: Drill and Rout
For the long skinny octagonal rod, you should drill a hole just wide enough for a piece of paracord to pass through. I drilled a slightly wider hole first using a small Forstner bit, to accommodate the knot I planned to make.
For the stumpy octagonal rod, you need to make a groove in the center to hold the paracord. The rod will end up looking like a yo-yo. I made it with a square bit on my router table but it would be easy to do on the table saw, too. I cut the groove about 3/4" (18 mm) deep and about 3/4" wide, taking about 1/8" (3 mm) out at a time.
You also have to drill the same sort of hole as you did for the long skinny rod, but in the bottom of the groove.
Now put a roundover bit in your router and smooth all the corners (both types of wrist roller). If you don't have a router table, just rasp and/or sand the corners down.
I needed a pin so the rollers could hold different amounts of weight, so I made a mini-rod about 2 1/2" (60 mm) long and 7/8" in diameter (22 mm) with the same sort of hole as in the large one. It got the same roundover treatment as its big brother.
Step 6: Finish and Add Weights
We sanded, pre-stained, stained and clear-coated (3 times) the rollers, and lightly sanded between coats. The rollers are very smooth as a result but there is plenty of grip thanks to them being octagonal in cross-section rather than round.
To add weight to the wrist roller, you can tie it to just about anything. A one gallon milk jug filled with water would work well. So do barbell weights, which is why I made the pin. We had an old weight lying around that was used by the previous owners of our house as a doorstop, so I used that for one of the wrist rollers. The cord is paracord, with a melted knot to prevent unravelling.
Step 7: Forearms of Steel
To use, just rotate the rod. Your forearms get both a concentric and eccentric workout (i.e. it hurts both rolling the weight up and down). A light weight is initially easy but the burn soon kicks in. Above shows the boys putting in an impressive number of reps. Count them, and try to beat their record!
For other wooden workout aids, check out my plyometric box.