Hold one runner in each hand with their ends pointing toward each other. One runner should have a slot in its end and the other runner should have a tab.
Push the two main runners together until they lock into place. Gently tug them to make sure they do not come apart. Lay the runners down on the floor.
Measure the length of room the runners need to span. Transfer this measurement to the two connected runners. Cut them to the appropriate length with a tin snips. Have a friend help you lift the runners into place, with each end resting on the perimeter molding.