The process of determining the true meaning of wills to give effect, as far as possible, to the testator's intention expressed in the will (see intention of testator). Generally the words used are given their ordinary grammatical meaning. If the words used are ambiguous, either in themselves or in the light of surrounding circumstances, extrinsic evidence may be admitted to assist in ascertaining the testator's intention. The process of construing a will by reference to the circumstances surrounding the testator when he made his will is commonly known as the armchair principle. Such evidence may not be used to contradict a clear expression in the will. The golden rule is to adopt a construction that will avoid an intestacy, on the basis that if the testator went to the trouble of making a will, he presumably did not intend to die intestate. There are also many detailed rules relating to the meaning of particular phrases and to imprecise gifts for charitable purposes.