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The Dark Ages
In early power racks you would see thick bolts or pegs going through the rack and sticking out to hold the bar. Some sort of head or lip on the end of it served to stop the bar from rolling off. Above is an example on a vintage York rack.
What appears to be those same pegs are still made for the Starting Strength Power Rack above. It’s an odd throwback.
Body Solid makes similar ones for their cheapest racks. A ball lock pin secures the rear end of the peg from slipping out.
The round peg crushes your bar knurling with its very small contact area against the bar. Back in the day, the overwhelming majority of bars in home gyms were cheap and not worth protecting. Now that people are paying more attention to the quality of bars, and the price has come down on them, protecting the bar has become a higher priority for people.
More thought is put into the shape of these than the earlier pin designs.
They are made with a flip-down design, like most rack attachments now. Stick the peg through, and the C-channel secures over the rack as you flip it down. This eliminates the need for safety locking pins to secure the peg on the back side.
Note that Rogue and some others call them J-cups, while others call them J-hooks. Same exact thing. A “cup” sounds more protective, doesn’t it? Good marketing word.
Anyway, a J-hook has a wider contact area against your bar than a round peg. This leads to less severe pounding-in of the knurling, but it also leads to scratches over a larger area, shaving off the knurling. All in all, I don’t think it’s better in this respect. Steel-on-steel is never a a good thing for durability.
Notably, they do have a backplate for you to walk the bar into to rack it, so you don’t drop the bar into the lip of a peg every time in that unnerving way.
There is one possible disadvantage to J-hooks vs the simple pegs. A peg holds the bar at the same height you stick the peg through. The J-hook holds the bar several inches lower. If you happen to be well over 6ft tall and you’re using a shorter squat rack like the Rogue SML-1, you could run into a problem with the max bar height.
UHMW Plastic Lined J-Hooks
This is a valuable upgrade over all-steel J-hooks. The inside of the J-hookshave UHMW plastic liners to protect your bar’s knurling and reduce noise.
You should wonder whether a plastic is suited for this job. This type of plastic is very hard and very durable and has withstood the test of time in this application. It will not crack, even with a loaded bar slammed down onto it, and it takes a lot of abrasion from rough knurling to make a mark in it.
Normally the wear against the plastic, or against all-steel J-hooks for that matter, comes from you rotating the bar as you try to slide it back centered after racking it, digging the knurling into the surface.
The proper term in industrial applications for this material is UHMWPE, ultra high molecular weight polyethylene. In the gym equipment industry it has gotten shortened to UHMW, or UHMW plastic. There are others such as HDPE, high density polyethylene. UHMWPE is the strongest.
As you can see in the pic of Rogue’s above, the back inside of the C-channel has a UHMW plastic liner as well, to protect the rack and reduce clanging noise.
However, check out this problem…
Most UHMW lined J-hooks, including Rogue, do not protect the front lip of the cup. So if your bar rolls forward to the lip, which is normally where you want it for unracking, then you’re scratching up your bar. There’s room to line the lip too. They choose not to do it to save on costs.
There are also sandwich J-cups, which are fully protected, but I’m talking about those further below.
Warning: Some J-hooks are “upgraded” with a strip of some thin protective tape like the above, which is trash and will wear out quickly. In one diagram, they say this tape is only meant for protection during shipping, which is nonsense because of where it’s placed, and the way all their pictures include it. They’re trying to pass it off as protection for your bar while at the same time absolving themselves of any claim that it works.
Best Modern Design: Sandwich J-Hooks
What are these “sandwich” J-hooks, why are they more expensive, and why does anyone want them?
That’s what I thought when I first ran into them online. What’s wrong with other J-hooks? Well, I’ll tell you.
A thick chunk of UHMW plastic is sandwiched and bolted in between two thick steel plates in a way where the plastic sticks out all over. This design has a couple major advantages.
First, if you re-rack too low, into the bottom front of the J-hook, you’re still only hitting the plastic, not steel like you would with regular J-hook that only have plastic liners on the inside of the hook. It’s also so tall that if you rack the bar a few inches too high you’re still on the J-hook.
Second, the thin design of sandwich J-hook (it’s only 1.5″ thick side-to-side) gives you more room for side-to-side slop when racking the bar. That puts you at far less risk of hitting the shoulder of the bar on the J-hook as you rack the bar and trying to glance to your side to see what’s going on. You gain on an inch or two of room on both sides. The hook protrudes far enough from the rack that the bar shoulder will not hit the rack’s steel upright.
While your bar is the #1 thing to make sure you like, because it’s the thing you’re directly handling, the J-hooks of a rack are #2, because they control how easy it is for the bar to interact with the rack.
Several manufacturers make these. Rep Fitness makes good ones that are 100% compatible with Rogue racks at less than half the price of Rogue. Specifically, Rep’s PR-4000 sandwich J-cups fit Monster Lite racks, while their PR-5000 sandwich J-cups fit Monster racks. And while it’s not clear on the product page, yes, they are sold in pairs. Normally Rep’s pricing is closer to Rogue, as their quality is about the same, but in this case it’s a steal.
Other brands have lousy cross-brand compatibility. They need to fit right. See the power rack accessories and compatibility guide.
Rogue makes some extra-thick 2″ sandwich J cups for their Monster racks. I don’t think the weight capacity is any issue on the smaller ones. I think it has more to do with these thicker ones are made with the hardware recessed into the design so that no bolts are sticking out, for a cleaner look and no potential of the shoulder of your bar hitting a bolt.
The Right Fit
Unlike some other power rack attachments, J-hooks need to be made to fit snugly on your exact rack or one the same size as it. This includes both the tubing size and the hole size.
It’s a safety issue. I don’t recommend messing around with jerry-rigging J-hooks.
That being said, if you’re a chronic DIYer and good with your hands, cutting some shims from UHMW plastic sheets is the best way to fit oversized J-hooks on smaller tubing.
One More: Roller J-Hooks
A couple companies just started producing these regularly.
These are from Bells of Steel. The nylon sleeves spin over a steel pin. The sizing is so unique that they will only fit Bells of Steel racks.
I imagine the idea has been around for a while. I saw a clip of Alan Thrall some time back building some steel ones into his olympic bench. The idea with roller J-hooks is you can very easily center the bar before each set.
The nylon rollers I haven’t seen before. I guess it’s strong enough. My guess is that’s a 5/8″ steel pin inside there, the same material used for the rear peg going through the rack, and at just a few inches long it ought to hold up fine to the weight of a barbell slammed onto it?
Titan Fitness has three sizes of roller J-cups for their different lines of racks. They have a better lip in front and UHMW inserts. Same basic idea though with the nylon rollers.