Markers are used to help cross-reference various information within the plans. They are used as pointers to tell you where to go to find the information you may be looking for.
An elevation marker has a arrow pointing to the face of the building it is referring to. The example to the left is pointing to the south face of the building and is labelled "S" for south.
It also has a page reference to tell you which page to look at.
A section marker indicates where the building is being sliced (like a loaf of bread) and which direction you are looking once that slice is made.
It also tells you what page to look to and where on that page you will find the section drawing.
In the example, you can see a man who is looking at a table. In the section drawing, you can see the table as well as all the building components that have been sliced through. In order to find that drawing, you would need to look at Section A
on page A-300.
A detail marker is made up of a larger bubble that indicates the content you can expect to see within the detail drawing.
It also has a page reference to that detail, and a location within that page.
The example to the left is of a rim joist detail which can be found at location "2D" on page A-500. You can see that there is a much higher level of information shown on the close-up detail.