Construction prop

A prop comprising:

• an outer tube, a top end of the outer tube having a threaded section;
• a pair of slots being axially formed on the threaded section of the outer tube;
• an inner tube telescopically fitted in the outer tube, the inner tube being formed with several pairs of pinholes axially arranged at intervals;
• a locating nut screwed on the threaded section of the outer tube;
• a controlling member which is a collar member;
• a pair of through holes being radially formed on the controlling member, two recessed/projecting structures being formed on a top face of the controlling member at equal intervals, each of the recessed/projecting structures having a standard position, a releasing position lower than the standard position and formed on one side of the standard position, and an adjoining face connected between the standard position and the releasing position;
• the controlling member being fitted around the outer tube, a bottom end of the controlling member being undetachably and relatively rotatably connected with a top end of the locating nut;
• and
• an insertion pin which being able to be fitted through the slots of the outer tube and inserted in one pair of pinholes of the inner tube, and the insertion pin being rested on the top face of the controlling member;
• alternatively, the insertion pin being able to be fitted through the slots of the outer tube and inserted in one pair of pinholes of the inner tube and the through holes of the controlling member;
• each of the recessed/projecting structures of the controlling member further has an inclined guide face, the guide face having a higher end and a lower end, the higher end of the guide face adjoining with another side of the standard position, the lower end of the guide face adjoining with the releasing position of the other recessed/projecting structure;
• and
• the higher end of the guide face is higher than the standard position.