Building site edge safety guardrail

The utility model relates to the technical field of building sites, in particular to a building site edge safety guardrail which is characterized in that long grooves are formed in the opposite side faces of two supporting rods, two long plates are placed between the two sets of long grooves, sliding blocks are fixed to the two sides of the lower long plate, and placing grooves are formed in the two sides of the upper long plate; a connecting rod is fixed at the center of the lower surface of the knob; a gear is fixed at the lower end of the connecting rod; sliding grooves are formed in the upper surface and the lower surface of a placement groove in two sides of the gear; limiting blocks are placed in the sliding grooves in two sides of the gear; the two long plates are slidably connected through the long grooves in the supporting rods, the vertical rods are inserted between the two long plates, the two ends of the upper long plate drive the limiting blocks through the gears to move to penetrate through the