A more thorough explanation:

The Rule in Shelley's case is a legal principle that applies to certain future interests. It prohibits the conveyance of a future interest to the heirs of the grantee who received the possessory estate. If the grantor tries to convey a future interest to the heirs of the grantee, the interest is considered to be to the grantee and not in the heirs of the grantee.

For example, if John grants land to Mary for life, with the remainder to Mary's heirs, the Rule in Shelley's case would apply. Mary's heirs would not receive the remainder interest because the interest would be considered to be in Mary and not in her heirs.

Another example would be if a father grants land to his son for life, with the remainder to the son's heirs. The Rule in Shelley's case would prevent the son's heirs from receiving the remainder interest because the interest would be considered to be in the son and not in his heirs.

These examples illustrate how the Rule in Shelley's case works by preventing the conveyance of future interests to the heirs of the grantee. Instead, the interest is considered to be in the grantee and not in their heirs.