收发钢材要测量钢材的长度,测量超过2～3米以上的钢材,要两人拉皮尺才行。可根据步枪射击时瞄标尺、准星和目标三点一线的原理制作一测长器来进行测量。做标杆,与测量对象垂直,杆长为1400毫米,杆底为测量的起点,杆顶为瞄准点,自杆顶向下28毫米处,顺测量方向,设标尺与标杆垂直,标尺每20毫米画一格,标杆高 Sending and receiving steel to measure the length of steel, measuring more than 2 to 3 meters of steel, two people to pull the tape. A measuring device can be made based on the principle of aiming ruler, sight and target at the time of rifle shooting. Do benchmarking, perpendicular to the measuring object, the length of the rod is 1400 mm, the bottom of the rod is the starting point of measurement, the top of the rod is the aiming point, and the top of the rod is 28 mm from the top of the rod. Follow the direction of the measurement. Set the scale to the vertical of the rod. The scale is every 20 mm. Draw a grid, high benchmark