An organisation consists of superiors and subordinates. The formal lines of authority from highest to lowest ranks are known as scalar chain. For example: Let us consider a situation where there is one head ‘A’ who has two lines of authority under her or him. One line consists of B-C- D-E-F. Another line of authority under ‘A’ is L-M-N-O-P. If ‘E’ has to communicate with ‘O’ who is at the same level of authority then she/he has to traverse the route E-D-C-B-A-L-M-N-O. This is due to the principle of scalar chain
However, if there is an emergency then ‘E’ can directly contact ‘O’ through ‘Gang Plank'. This is a shorter route and has been provided so that communication is not delayed.