Final answer:
The tubular type jack stand is locked by means of a steel pin that is inserted into a hole in the tube.
Step-by-step explanation:
The tubular type jack stand is locked by means of a steel pin that is inserted into a hole in the tube. This steel pin secures the jack stand in place and prevents it from collapsing or moving while in use. The pin is typically inserted through a series of holes in the tubular frame and then through the corresponding hole in the support arm.