When you put buttons on a slide, they will usually lie above parts of the text in the fields of your slide. When this happens, it becomes difficult to edit that text without moving the buttons, which is a nuisance at best.
Click on this button when you wish to edit the text in one of your fields after you have put buttons on the slide. It will temporarily hide all your buttons and un lock all your fields for immediate editing. When you are through editing the text, click on this button again and it will lock all your fields and restore all your buttons to the state they were in just before you clicked the first time.
This button can be a real life-saver when you are in the middle of delivering your lecture or presentation and discover an important typo in one of your fields, since using this button will allow you to correct the error simply, and without a lot of fumbling.
Be aware, however, that changing the text in a field may change the location of other parts of the text in relation to buttons. The result is that a button that used to work fine to hilite a certain word may hilite some other word, or part of a word, which has moved to that location instead.
By far the best plan is to eliminate all typos before delivering your lecture.
