The most sturdy suitcases are generally constructed from polymers such as nylon and have a covering that resists gouging and liquid from entering into the interior. The seams can be glued together or stitched with strong nylon thread. Generally the stitched-together suitcases hold up over time as compared to the glued construction and have a lock or latch.
Many modern suitcases have built-in small wheels enabling them to be pulled along on hard flat surfaces by a fixed or extendable handle or by a retractable or stowable leash. Suitcases are a type of luggage. A smaller, firmer suitcase, used mainly for transporting papers and office supplies is known as a briefcase. Some cases are made from proprietary materials such as Cordura or Tegris.