Then you may find the "narrow-to-region" command useful too. It allows you to select a region of text, and make everything else in the buffer invisible and unm

Then you may find the "narrow-to-region" command useful too. It allows you to select a region of text, and make everything else in the buffer invisible and unmodifiable. I find it useful when trying to grok a specific function without getting distracted, or more usefully, doing a search-and-replace without fear of doing a replace in an unintended part of the buffer.