Do i need a biscuit jointer

[festive]

Im fitting some decking which apparently needs a 4mm slot cut for the biscuits, i see screwfix etc do these slot cutter tools for a router.. can i just use one of this instead on my router. What's the difference advantage of using a buscuit jointer?

 

[ladylola]

For a small project like yours then the router bit would be the way to go in my opionion.
I think the biscuit cutters are better for someone doing a lot of that sort of work as they seem easier to set up repeatedly and are perhaps a bit easier to physically hold and use too.

 

[big-all]

dowels and biscuits are usually made from beech and beech is not very good in wet situation as it rots
what use are they for