Hollow rock

Does anyone know what hollow sounding rock actually looks like underneath the surface?  Is it usually filled with pores? Hollowed from lizard people? 

It's typically weaknesses and fractures on the point that connects the piece of rock to a larger body of rock. It can be barely visible to a large void.

It's not usually hollow, per se, but is in my experience a flake or jug that is attached with much less rock than it first appears.  It will sound more hollow the farther away you tap from the actual point it is attached.  I hope that makes sense.

Adam Orton wrote:

I find that the standard knocking of a "shave and a haircut" with the usual response of "two bits" works well. Anymore than that and I steer clear. 

I'm trying to wrap my head around what you just said and I can't figure it out. What does this mean?

BigRed11 wrote:

I'm trying to wrap my head around what you just said and I can't figure it out. What does this mean?

@ 0:10, that is what OP is doing to a flake, but the funny part was that they would do the first "shave-and-a-haircut" part and the rock would reply "two-bits!" if it wasn't going to break. At least that was my interpretation of their comment. 

holy shit haha

I've heard that knocking pattern enough times that I'm convinced it's ubiquitous, but I'd never encountered the "shave and a haircut" phrase. Is that the origin of the knocking pattern? I know this is off topic.

David Kerkeslager wrote:

I've heard that knocking pattern enough times that I'm convinced it's ubiquitous, but I'd never encountered the "shave and a haircut" phrase. Is that the origin of the knocking pattern? I know this is off topic.

I've heard that it dates from a century or two ago. A barber (or maybe just someone that owned a razor and scissors) would knock this pattern on hotel room doors. If you wanted a shave and had a spare 50 cents you answered the door. If not, you ignored it and the barber would move on to the next door.

In regards to the OP: it isn't necessarily hollow, it just isn't fully attached. A flake that is attached along only one edge can flex in such a way that it might not hold any a pro. An active cam could potential exert enough force during a fall to detach the flake from the rock face.

Edit: It is the lack of a solid attachment that gives it a hollow sound--something that you won't hear just knocking on the main body of rock.