"As most tracker mortgage rates are linked to the Bank of England base rate, it can be easier to predict whether they are likely to rise or fall compared to other variable deals, which are set at the lender's discretion. This is because there is usually lots of coverage on potential base rate changes in advance, so you may be able to prepare for increases. Of course, you can never be completely sure on what the Bank of England may change the base rate to, so it's always worth being sure you can afford payments if it was to suddenly increase."
Also known as an interest rate floor, it's the rate in which the interest on your mortgage can't fall below - even if the base rate does.
For example, if your lender has set a collar rate at 1.5% and the base rate falls to 1%, the interest you pay on your mortgage will still be 1.5%.
Not all tracker mortgages have a collar rate, so check with your lender first.