Do you mean Cloche? As in something you put over plants or soil to raise the temperature?
If so, it would depend on how big you want it to be and what shape. I use a bell cloche about 35cm tall and 35cm wide at base tall to go over my small seedlings. If you wanted something a similar size. you could make a teepee structure from bamboo cane or green canes, and bind them firmly at the top, and then bind shorter lengths of green cane at the bottom.
Then you can attach the polythene to the canes.