Clicking on the left-pointing arrow will take you back to the submenu of the section you are currently in. Clicking on the right-pointing arrow will just take you to the next item in the section, until you eventually reach the Order Form.Clicking on a button in the left-hand frame will take you to a particular section of the catalogue - e.g., clicking on KITS will take you to the KITS section.
Within the sections there are submenus which are there for you to choose, for example, which particular Kit you wish to look at.
There are also arrows - Clicking on the left-pointing arrow will take you back to the submenu of the section you are currently in. Clicking on the right-pointing arrow will just take you to the next item in the section, until you eventually reach the Order Form.