We had something called an ‘acceptgiro’, it was basically a pre-filled money transfer order. Usually the amount, beneficiary and some reference number were pre-printed. All you had to do was sign it and mail it to the bank (which usually was free, you had pre-paid envelopes from the bank). It was usually attached to the bill, basically a tear-off part of the bill that you signed, stuffed into an envelope and mailed.

For recurring payments you usually give the other party ongoing permission to directly take it from your account. This is still extremely common and how I pay 99.999% of my bills. For things like mortgages, rent and insurance it’s usually required to pay in this way. Basically, my monthly bills get paid without me even having to think about it.