The Apollo lunar module had thin skins of foil for protection / air containment. What would have happened if a hole was made in this skin by a flailing astronaut, screwdriver, asteroid, etc.? Would the tear have gotten larger and larger before it could be patched?
A hole in the LEM during lunar operations would likely have been grounds to abort, and return to the CSM. For the flight up, it's known that duct tape was carried in the LEM; Apollo 17 made use of it repairing their rover, and proved it's ability to hold in high quality vacuum. It's thus very likely that they'd have patched a single small hole or pair of small holes with duct tape from the inside, and checked for pressure. It's almost certain such a repair would still have them make the trip in suit, ready to button up immediately.
A hole in the CSM might be more of an issue, since large portions of the pressure vessel are inaccessible during flight. If such an inacessible hole happened, it's likely the crew would have gone to suits, on umbilicals, and taken the very next opportunity to aim for Earth. An accessible hole would have been patched with duct tape or better materials.
Further note: the Apollo astronauts had a suit repair kit; it would likely have been used in the case of a breach.
Keep in mind: the wall thickness was 0.012 inches (≅0.305mm); this is about 3.8x the thickness of a typical soda can (≤0.1mm), and those are not easily holed (it tends to deform rather than puncture). Further, the internal pressure makes the skin rigid, just like a soda can; a can of 7-up is 30psi, and a standard atmosphere about 14.7 - so a soda can is thick enough to hold in 1 atmosphere. The walls of the LEM are three to four times thicker... thus harder to pierce, and less likely to tear if punctured.
The Saturn/Apollo Stack - Lunar Module (http://h2g2.com/approved_entry/A3770192) Retrieved 2 Aug 2013.
Pressure in a Can of Soda (http://hypertextbook.com/facts/2000/SeemaMeraj.shtml) Retrieved 2 Aug 2013.