The sleepers in the form of two bowls placed under each rail and connected together by a tie - bar are known as:

Explanation:

Pot sleeper:

• Cast iron pot sleepers consist of two hollow bowls or pots of circular or elliptical shape placed inverted on the ballast section.
• The two pots are connected by a tie bar with the help of cotters and gibs, the gauge can be adjusted slightly (± 3 mm or 1/8") by changing their positions.
• The rail is placed on top of the pots in a rail seat provided with a cant of 1 in 20 and is held in position with the help of a key. The pot sleeper suffers from the drawback that it cannot be used on curves sharper than 4° on BG.

Box sleeper:

• Box sleepers are in a box shape. Box sleepers are no longer being used in the modern construction of railway tracks.

Plate sleeper:

• These consist of rectangular plates. Projecting ribs are provided at the bottom of each plate sleeper for lateral stability. These connections are similar to pot sleepers. Pot and plate sleepers are with flat-footed and bull-head rails.

Duplex sleeper:

• These sleepers are used in conjunction with CST-9 sleepers. These sleepers are used on rail joints to prevent cantilever action between two supports of CST-9 sleepers.