Corrected entry: When Embrey is talking with Hancock in jail via the telephone intercom, they're facing each other through wire mesh reinforced glass. Hancock uses his fingernail to score a circle in the glass and then taps it out as a perfect circle. This type of glass would not tap out with scoring, since there's a wire mesh bonded between two layers of glass. At most he would've dislodged the interior pane and shattered the exterior pane.
Andrew Upton
20th Jan 2009
Correction: Hancock has nails that with the lightest pressure have cut through the glass - I'm sure with this and his strength cutting through the metal wire beneath at the same time would be no problem.
Andrew Upton