This sequence repeats itself until the last step in the chain is completed and a terminal reinforcer (the outcome of a behavior chain, i.e. with brushing one's teeth the terminal reinforcer is having clean teeth) is achieved.
Backward chaining is the procedure that is typically used for people with limited abilities.
Backward chaining is the preferred method when teaching skills to individuals with severe delays because they complete the last step and see the direct outcome of the chain immediately rather than having to be prompted through the remaining steps to receive that reinforcement.
The teacher begins by prompting the learner through the entire chain, starting with the last behavior.
The teacher repeats this until the learner can perform the last step without prompting upon the distinctive stimulus being presented.