Can Penetration Rings Be Used on Any Wall?

Hey, that's a really interesting question—combining futuristic gadgets with our current knowledge of renovation and construction. As someone who also grew up watching Doraemon, let me share my thoughts.

About the Anywhere Door, it's a two-sided story

Simply put, we need to distinguish between analyzing it within the world of Doraemon versus using real-world logic.

1. In the world of Doraemon: It’s practically "all-powerful"

Based on its portrayal in the manga and anime, the Anywhere Door is practically a game-breaking tool.

Almost no limitations: Whether it’s the wooden walls of Nobi’s house, the reinforced concrete walls of the school, or underground soil layers, it passes through them effortlessly. Its principle seems to create a "wormhole" between two points in space, rather than physically drilling a hole.
Thickness isn’t an issue: In several episodes, they use it to penetrate very thick ground or walls, suggesting its "penetration depth" is impressive.
Material doesn’t matter: Wood, brick, concrete, earth, stone... basically nothing stops it.

So, in the Doraemon universe, the answer is: Yes, it can be used on almost any "wall," where "wall" broadly means any barrier.

2. If we had it in the real world: Now that’s a different story

If we actually got our hands on an Anywhere Door for home renovation or "shortcuts," there’d be a lot more to consider. This ties into the tags you mentioned, like building materials and construction techniques.

First, consider the wall’s "composition"

Standard walls (brick, drywall): These would probably be fine—the ideal scenario for the Anywhere Door. Imagine going straight from the living room to the bedroom without detouring through the door.
Load-bearing walls: This makes me sweat. While the door creates a temporary passage that disappears after use, theoretically not damaging the structure... but what if? What if it affects internal stress during penetration, or the gadget runs out of power mid-use? Messing with load-bearing walls risks the entire building's safety. (In reality, you absolutely cannot tamper with load-bearing walls!)
Shear walls / Reinforced walls: These are packed with dense rebar. Would the door make the steel vanish within the passage, or would it jam upon encountering it? If it can pass through, its handling of metal would be miraculous. If not, its usability would be severely limited.

Second, consider the wall’s "contents"

Modern walls aren’t just barriers; they hide crucial systems:

Electrical wiring: Could penetration cause a short circuit? Or after the passage closes, might "severed" wires fail to reconnect perfectly, creating a safety hazard?
Water pipes / Heating pipes: Penetrating these could flood your home if not perfectly restored. A terrifying thought.
Network / Signal cables: Less critical—worst case, you lose internet.

Finally, and most crucially: You never know what’s on the other side

This might be the biggest "safety notice" for the Anywhere Door. Before placing the ring on the wall, you’d better be 100% sure what lies beyond.

A neighbor’s bedroom? Awkward.
A bathroom, and someone’s using it? Social suicide.
Someone’s safe? That’s a legal issue.
The building’s exterior, and you’re on the 30th floor? One step, and you’re in freefall.

To summarize my view

Theoretically (Doraemon’s world): The Anywhere Door is a divine tool—use it freely, no limits.
Practically (if it existed): It would be a high-risk "professional tool" requiring thorough preparation. You’d need to act like a pro contractor, understanding the wall’s structural type (is it load-bearing?), internal utility layout, and what’s on the other side.

So, while the Anywhere Door seems amazing, using it would be far more complex than we imagine. If this treasure existed, its instruction manual would probably be thicker than my property deed!