A wooden frame built especially to support the sides of an arch until the keystone is positioned.
支拱板条专门用来在拱顶石放置好以前支撑拱的两边木架子。
2
In this dissertation, the keystone of Differential Interference Contrast Microscope is analyzed, and the optics and machine frame of Microscope is illuminated briefly.
本文首先详细分析了微分干涉相衬显微镜的光学系统原理，然后对显微镜光机结构做了简要分析。
3
The joint of a frame is the keystone in structural design, the stress with a complicated distribution were concentrated in the connection, that makes the node difficult to be designed and constructed.