求翻译：檩条安装:檩条截面较小，重量较轻，采用一钩多吊或成片吊装的方法吊装.檩条的校正主要是间距尺寸及自身平直度。间距检查用样杆顺着檩条杆件之间来回移动，如有误差，放松或拧紧螺栓进行校正。平直度用拉线和钢尺检查校正，最后用螺栓固定是什么意思？

Purlin installation: purlin cross-section is smaller, lighter, using a hook more than hanging or into a piece lifting lifting the purlin correction is pitch size and flatness. Spacing check the kind of rods along the purlin rod moves back and forth, if error, to relax or tighten the bolts to be corr

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Purlin installation: Purlin cross-section of smaller, lighter, using a hook hanging or flakes lifting method for lifting. calibration of Purlin mainly spacing and its flatness. Spacing between check sample along the Purlin Rod moving back and forth, if there are errors, relax or tighten the bolt to