Which component must be free from illegal drills or welds according to inspection standards?

The frame of the trailer must be free from illegal drills or welds because the structural integrity of the trailer is essential for safe operation. Any unauthorized modifications such as illegal drills or welds can weaken the frame, potentially leading to catastrophic failures while on the road. This can compromise the load-bearing capacity and overall safety of the trailer. Inspection standards prioritize the condition of the frame, as it supports the entire structure and ensures that it can safely handle the loads it is designed for. Maintaining the frame's integrity by ensuring it is free from improper modifications is crucial for the safety and compliance of the vehicle.