The wagon with opening roof is a type of railway goods wagon that is, nowadays, defined and standardised by the International Union of Railways (UIC) as Class "T". They are a large category of rail vehicle, predominantly used for the transport of hygroscopic bulk commodities such as cement, plaster, lime, potash and grain.

Goods wagons or freight wagons, also known as goods carriages, goods trucks, freight carriages or freight trucks, are unpowered railway vehicles that are used for the transportation of cargo. A variety of wagon types are in use to handle different types of goods, but all goods wagons in a regional network typically have standardized couplers and other fittings, such as hoses for air brakes, allowing different wagon types to be assembled into trains. For tracking and identification purposes, goods wagons are generally assigned a unique identifier, typically a UIC wagon number, or in North America, a company reporting mark plus a company specific serial number.