This is a test of commonsense. Complete the next sentence:

How to measure a straight line distance using a topo map
Lay a piece of paper down on the map and mark it.
Place a straight edge of a piece of paper onto your map. Line up the edge with both the first (" point a ") and second (" point b ") points you want to measure the distance between, then make a tick mark on the paper where each point is.
Make sure your piece of paper is long enough to make your 2 tick marks. Note that this method works better for shorter line distances.