These structures are built by a machine steered by gripper shoes attached to thrust cylinders; that machine is the Gripper TBM. Peter W. Barlow patented a shield used in conjunction with compressed air to protect new portions (20[1])of these structures, which must be reinforced within their stand-up times. (0[1])A method (0[1])for venting (0[1])noxious gases from these structures (0[2])was developed by Clifford (0[1])(*) Milburn Holland, (10[1]0[1])who oversaw the construction of many of them in New York City. (10[1]0[2])The cut-and-cover (0[1])method (0[2])for building (10[1])these structures begins (0[1])with digging (10[2])trenches. (10[2]0[2])Modular construction (10[1]0[1])of these structures (10[1])can be performed with immersed tubes. (10[2]0[1])The Boring Company produces, (10[4]0[2])for 10 points, (0[1])what cylindrical underground passageways that can house subway systems? (10[2]0[1])■END■ (10[15])