Expanding the idea of how price action develops on individual bars to a group of bars starts to paint a picture of what trend is doing. When price is breaking below buy orders we had to have more sell orders to do this. So we can say where we had buy orders is now sell orders. Look left is a common phrase in supply and demand, it refers to an area of orders where we suspect we could trade from. Using the daily these orders are easier to spot, smaller time frames are more difficult. When you are looking left we want to find the initial point price stopped moving lower - price stopped moving lower because it encountered buy orders and when price runs over these buy orders, it was for the simple fact we had more sell orders. This line marks supply, the area above the line marks the supply area.
