of safes. These are tightly guarded by both the manufacturers and locksmithing professionals. Drilling is usually aimed at gaining access to the safe by observation or bypass of the locking mechanism. Drilling is the most common method used by locksmiths, and is commonly used in cases of burglary attempts, malfunctioning locks or damaged locks. In observational attacks, the drill hole allows the safecracker to view the internal state of the combination lock. Drill-points are often located close to the axis of the dial on the combination lock, but observation may sometimes require drilling through the top, sides or rear of the safe. While observing the lock, the locksmith manipulates the dial to align the lock gates so that the fence falls and the bolt is disengaged. Bypass attacks involve physical manipulation of the bolt mechanism directly, bypassing the combination lock. All but the simplest safes are designed to protect against drilling attacks through the implementation of hardplate steel (extremely wear-resistant) or composite hardplate (a casting of metal such as cobalt-vanadium alloys with embedded tungsten carbide chips designed to shatter the cutting tips of a drill bit) within the safe, protecting the locking mechanism and other critical areas such as the locking bolts. The use of hardplate ensures that conventional drilling is not successful when used against the safe. Drilling through hardplate requires the use of special-purpose diamond or tungsten-carbide drill-bits. Even then, this can be a time-consuming and difficult process with safes equipped with modern composite hardplates. Some high-security safes use a glass relocker. This is a piece of tempered glass mounted between the safe door and the combination lock. It has wires attached to the edges. These wires lead to randomly located, spring-loaded bolts. If an attempt is made to penetrate the safe, the penetrating drill or torch could break the glass and release the bolts. These bolts block the retraction of the main locking bolts. To drill a safe with a glass relocker, side, top, or rear drilling may be necessary. A gas abrasive drill can sometimes be used to drill through a glass relocker without triggering it. Many modern high-security safes also incorporate thermal relockers in conjunction with glass-based relockers (usually a fusible link as part of the relocker cabling), which also activate when the temperature of a safe exceeds a certain level as a defense against torches and thermal lances. Drilling is an attractive method of