Hi. In a reading comprehension called " How to prepare a foundation for a brick wall" there is written "Place pegs in the floor of the trench and stretch a line between them". What does "the floor of a trench" mean ? I thought it means the bottom part of a trench, the dug part. Instead, there is a picture next to the text that shows those pegs around the trench (on the ground floor, not in the bottom) and the line above the trench. So what does "the floor of a trench " mean?