This is a very old tip, but unless you’re aware of it you can quite easily miss it. I only mention it because it has come to my attention during recent discussions that it isn’t commonly known.
During sketch mode, either in the Project Environment or Family Browser, when Chain is selected (on the Options bar), the ability to constrain a line (when drawing aligned to another element) by clicking the little padlock is removed. The padlock appears when you make your second click but as you move your cursor it disappears again. I realise there are other alternatives, such as Pick Lines with Lock selected, but occasionally this is the preferred option. To resolve this and have the padlock remain accessible for selecting before drawing your next line, just make sure that Chain is unselected.
Happy Sketching makes for a betterRevit!
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