Originally Posted by picardo
I'm making a sitemap using Garret IA stencils. I decided I want to give the lines arrow ends. I selected all the lines, but couldn't figure out how to make them arrow heads all at once. Other than doing it one by one, is there another way of doing this?
However, it is difficult for me to answer your question precisely because Just how much you have progressed in your effort is unclear:
1 If you have "selected all the lines" that you wish to change, then simply use the Inspector/Lines&Shapes to change any property (including arrowhead ), while the desired lines to be changed are Selected, it will change the selected lines (refer attachment).
2 but I doubt that your question is that simple, and I suspect you have difficulty selecting just the lines you want to change (without having to Select each line manually), and excluding others. For that it is helpful to understand the Canvas/Selection Inspector.
• an entire group of lines (in the current Canvas) can be Selected by selecting a "well" in this Inspector.
• multiple "wells" can be selected via ⌘click or ⇧click
• the lines/shapes that are collected into a "well" is controlled by SortUsingStyles drop-down in the same Inspector
Once you have made the "wells" contain the Lines you want (and exclude those you don't want); or you choose the Lines you want via multiple "wells", then simply change any of the Line properties as per  above.