The 'F9' button located on the toolbar at the top of the page can be selected by using the corresponding 'F9' key on the keyboard or by using a mouse click.

F9 - Prev (Record)

When this button appears in the toolbar, you can select 'F9 - Prev' to move you to the previous record in the database.

(This function is only available when the record is being viewed in a non-editable state, i.e. Before you have accepted into the record)