Bisects means a stamp that has been cut to be used for a lesser postage value than its face. For example, a 10 pence stamp may be cut in half and used as a 5 pence stamp. This was permitted long ago, but it is no longer allowed.
There are three types of bisects Horizontal, Vertical and Diagonal. Bisecting was done in emergencies when no stamps of the lower denomination were available.
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