The examination of the bullet wound can help determine whether the muzzle of the gun was pressed against the victim's body, the type of weapon used, and where the bullet entered and exited the victim's body. Much can be learned of bullet hole entrances and exits or the presence of powder burns by examination of clothing. Damage to glass caused by a bullet can tell which side of the glass was struck by the bullet. Bullet direction can also be determined by an examination of wood and metal the bullet struck. Evidence should be carefully removed from the crime scene so as not to damage it, and at the ballistics section, the evidence should be weighed, classified by caliber, and marked for future identification. An examination of a weapon should yield information on classification as to caliber, manufacturer, type and model, serial number, length of barrel, number of chambers, and finish. If the gun is a semi-automatic, the overall length and magazine capacity should also be recorded. The weapon is also examined to determine whether it shows any signs of discharge. Test firings of the weapon yield information on the direction of twist and the amount of lands and grooves of the test bullets. The analyst should consider class characteristics determinable prior to manufacture and use. They originate in peculiar features of design, operation, or construction in the mass manufacture of firearms. The analyst should next search for the identifying characteristics of the weapon determinable only after manufacture, such as wear, abuse, mutilation, corrosion, erosion, and other fortuitous causes.