Cov zawv zawg dav dav, zoo li galvanized txias-kuav los tiag steel rails, feem ntau yog siv rau hauv tsev tub rau khoom. Lawv muaj qhov xav tau qis rau qhov kub thiab txias tuaj yeem tiv taus 70 degrees, uas yog haum rau tib neeg. Txij li cov zawv zawg dav dav muaj cov hlaws yas, cov roj hmab nres thiab cov yas disassembly hauv cov qauv, yog tias qhov kub siab tshaj 70 degrees, cov khoom siv yas yuav mos, uas yuav cuam tshuam rau daim ntawv thov dhau sijhawm.