Thread Safe Template Library (TSTL) is a C++ library that provides thread-safe containers with high grade of locking. It includes classes for multimaps based on a B-tree and a hash table. It also includes classes for a queue, a priority queue, a pipe, an alloccache, a timercache, a limitcache without global locking, and a fast shared mutual exclusion locker (also known as "rwlock" or "wmrg"). It's useful for writing multi-threaded applications, network services, and operating system components with high requirements for interactivity level.