The bar can be a valuable representation to enable students to represent problems in such a way that the mathematical structure is exposed.

This enables students to ‘see’ the problem clearly and to then recognise the strategy they need to solve the problem.                                                                                                                                                                 NCETM

​

It is important to go through all the stages from concrete to pictorial to abstract at the start so that pupils can make sense of the problem and build up from something concrete to an abstract method that they can use fluently.