This specifically waives to exclude a relative or somebody else in the Will. One of them is that you just want to be explicit about excluding the person. You can state that you are deliberately leaving nothing to that person and therefore, that person can not make a claim; and just because they had a relationship they think that they should be entitled. However, you want to be extra careful that the person who is being left out of the Will, can not make a claim and that the Will was under duress or not done properly.
Sometimes it can be very hurtful to the person who is not in the Will and they will try and challenge it. So it is important that the Will is properly completed and the person is not under duress and also has the mental capacity to do so. It is fairly simple to document it.