The idea is to repeat several times the issues that you want the audience to remember so that it's easier for them. The ending needs to be your strongest, most compelling message. It is the grand finale of your message and needs to compel the audience to do something. The outcome may be selecting you for a project, selling a change order to an owner or convincing a subcontractor he needs additional safety precautions. End your presentation with a call to action.
Psychologists say that people remember things based on the laws of primacy and recency.
Primacy says that you remember the things that you hear, see or do first. Recency says that you remember the things that you hear, see or do last. So be sure that you have both a catchy opening and a strong close. Make sure that your opening and closing are the best parts of your message. The conclusion needs to be tied to the opening.