End face with a gap, no boss butt is refers to the upper and lower casing left a certain gap between the upper and lower main chord rod end face at the same time contact.
端面有间隙、无凸台对接是指在上、下套管之间留有一定间隙，上、下主弦杆端面同时接触对接。
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End face with a gap, no boss butt is refers to the upper and lower casing left a certain gap between the upper and lower main chord rod end face at the same time contact.