A more thorough explanation:

Definition: Insimul tenuit (in-sim-əl or in-si-məl ten-yoo-it) is a Law Latin term that means "he held together." It refers to a writ used by a coparcener to recover a fee tail that was alienated by a previous tenant. This writ is a type of formedon in the descender.

Example: If a father dies and leaves his estate to his two sons as coparceners, and one of the sons sells his share to a third party, the other son can use insimul tenuit to recover the fee tail that was alienated by his brother.

This example illustrates how insimul tenuit can be used by a coparcener to regain control of a property that was sold or transferred by another coparcener without their consent.