Never use this style of fuse holder for high current draw circuits. This type of fuse holder can be seen fitted on a number of vehicles when an optional tow bar is fitted by the manufacturer.
The add on equipment and fuse holder is not up to the task of supplying the power needed for trailer lighting. Once the terminals generate enough heat the fuse will begin to deform and melt along with the holder itself.
It may be some time before you realise the trailer lighting has stopped working.
This is a huge safety concern for all road users.
At Driven Auto Electrics we recommend checking your trailer lighting before you begin towing on each occasion.