This section is from the book "Real Property, An Introductory Explanation Of The Law Relating To Land", by Alfred F Topham. Also available from Amazon: The New Law Of Property.
The mortgagor surrenders his estate to the use of the mortgagee, or covenants that he will surrender it to him; but the mortgagee is not usually admitted, unless he wishes to foreclose.
The reason for this course is that fines are payable to the lord of the manor on every admittance, and these are therefore avoided if the mortgagee is content with a surrender.
If the money is paid off, he can re-surrender the land to the mortgagor, and no fine is payable at all (q).
If the mortgagee forecloses, he is then admitted, and the admittance dates back to the surrender, i.e. he is treated as having been the legal tenant since the date of the surrender.
The surrender is usually preceded by a covenant to surrender, containing the terms upon which the money is lent, the date of re-payment, rate of interest, etc. These clauses are very similar to the corresponding clauses in a mortgage of freeholds.
The student should read the form of a mortgage of copyholds on p. 328.
(q) Unless there is a special custom to the contrary.