Physical app blockers are small devices you tap or interact with to unlock the apps you have chosen to block, and the reason people buy them is simple: a button you can press is easier to press than an object you have to walk to.
A software blocker and a physical blocker both stop an app from opening. The difference is what stands in the way. With software, the thing between you and the app is a dialog, a timer or a setting - all of which you control, on the same device, in the moment you least want to be stopped. With a physical blocker, it is an object. If that object is in another room, getting past the block costs you a walk rather than a tap.
This is why people arrive at this category rather than starting in it. The pattern in reviews is consistent: someone tries the screen time limit built into their phone, learns they can dismiss it, tries a blocking app, learns they can delete it, and then looks for something that is not on the phone at all.
Devices you tap or carry: Scrolly, Brick and Bloom. They share the core mechanic - pick your apps, tap the device to block, tap again to unblock - and differ in price, in what the companion app does around the block, and in whether the device is built to be carried or left in one place.
Software-only tools sit next to this category rather than in it: Opal, Freedom, Screenzen and the screen time limit built into iOS. They do more in some respects, and they cost less or nothing. What they cannot do is put a physical distance between you and the decision.
Form factor decides more than the spec sheet does. A device that clips to your keys goes everywhere with you, which also means it is always within reach when you want to unblock something. A device with a magnetic base or a mount is built to sit in one room and stay there, which makes it harder to beat and useless away from home. Neither is better in the abstract; they suit different problems.
After that: whether the app charges a recurring fee or the device is a one-time purchase, how long the money-back window runs, whether it covers a laptop and tablet or only your phone, and what happens if you lose the device.
None of these is a lock. All of them can be undone by the person who bought them, by design - the point is to break the automatic reach for an app, not to confiscate a phone from its owner. Across reviews of every device in this category, the people who report the biggest change are the ones who put the device somewhere inconvenient on purpose.
This site collects reviews of one device in the category, Scrolly: video reviews, written write-ups and buyer feedback, each linked to its original. Two of those videos run a direct comparison against Brick.