Blanking or blinding refers to the absolute closure of a pipe, line, or duct. This is done by completely covering the bore with a fastened solid plate that is capable of withstanding the maximum pressure of the pipe, line, or duct without leaking.
Double block and bleed refers to the closure of a line, duct, or pipe by closing and locking or tagging two in-line valves and by opening and locking or tagging a drain or vent valve in the line between the two closed valves.