<human>:  What is the most efficient way to hang photos on a wall?
<bot>: The most efficient way to hang photos on a wall is to measure and mark the centre of the wall and the centre of each photo, then use screws and nails to hang the photos in the right places. Make sure you use screw eyes or d-rings on the back side of the frames to secure the photos. Also use a level to ensure the photos are straight.