Rabbit Run

Ahmed wants to build an outdoor run for his rabbit.
He has decided that it will go against one wall of the shed.
Ahmed has some wooden planks to use for the other sides of the rabbit run. Some are 4m long, some 5m and some 6m.
If he uses three planks, he will be able to make the rabbit run in the shape of a quadrilateral.
What quadrilaterals would he be able to make if he uses three planks the same length?
Why?
What quadrilaterals would he be able to make if he uses two planks the same length and one a different length?
Why?
What quadrilaterals would he be able to make if he uses three planks which are all different lengths?