Black Friday: lifetime access is on a special offer in the app, until November 30. Black Friday: special offer on lifetime access, until November 30. Download
건물의 구조에서 횡대는 중요한 역할을 합니다.Geonmul-ui gujoeseo hoengdae-neun jungyohan yeoghal-eul hamnida.In the structure of a building, the cross beam plays an important role.