Teflon tape or pipe dope can be used to create a seal on black iron pipe. Tim Carter of AsktheBuilder.com demonstrates how to do the job right and shares some helpful tips. This black iron pipe is used to transport natural gas to your furnace, water heater and stove. This pipe has threaded fittings at the connection point which need to be sealed with pipe dope or Teflon tape. Teflon tape should be wrapped onto the male end of the pipe in a clockwise direction. Pipe dope has the consistency of mashed potatoes. You just paint in on to the male end of the pipe. With both options, you need to make the connection and hand tighten then tighten again with a pipe wrench. Teflon tape and pipe dope will prevent natural gas from leaking. Watch this AsktheBuilder.com video for more details.