Introduced in the fourteenth century, the seat was originally stuffed with English wool, which, due to the importance of the wool trade, was a symbol of the nation's prosperity. Today, however, wool from the various nations of the Commonwealth is used, in order to symbolise the Commonwealth's unity.
The Lord Chancellor may speak from the Woolsack when speaking in his capacity of Speaker of the House, but must, if he seeks to debate, deliver his remarks either from the left side of the Woolsack, or from the normal seats of the Lords.
If a Deputy Speaker presides in the absence of the Lord Chancellor, then that individual uses the Woolsack. However, when the House meets in the "Committee of the Whole", the Woolsack remains unoccupied, and the presiding officer, the Chairman or Deputy Chairman, occupies a Chair at the front of the table of the House.
In front of the Woolsack is an even larger cushion known as the Judges' Woolsack. During the State Opening of Parliament, the Judges' Woolsack is occupied by the Law Lords. The seat, however, is by no means restricted to judges only; during normal sittings, any Lord may occupy it.