gst on renting of monsoon shed.

how to prepare eway bill in case of installation of monsoon shed out of state and for this sending of tarpolines and bamboo from state. Rent can only be determined after installation of complete monsoon shed in other state . hence it is difficult to value the trasaction at the time of preparation of eway bill. further after contract period of two or three years , materials are returned to state. how to treat the transaction ?
as there is no sale but renting income.