First, a deed of trust is a document that evidences a lien on property given as security for a debt. Deeds of trust require the use of a trustee and vary from state to state.
Second, a closed end is a single loan transaction with specific term of months or years, specific payment, and has no provision for future advances. A loan is called closed-end credit because there's a set date when all of the debt needs to be paid back in full, plus interest.
Sometimes, the borrower has the option to choose a loan set up as a closed-end or an open-end second mortgage. An open-end loan functions like a credit card where the borrower uses the credit line, repay and repllenishes the available credit (revolving) for future advances.
So a closed end deed of trust is a legal secured document for a non-revolving loan.
I hope the information helps.