Prep work before sanding a varnishing wood floors

[rich_vw]

Have a T&G timber floor that I intend to sand and varnish, we had to cut along the joint to be able to lift some of the boards to allow pipes and wires to be laid under the floor, now although this was done as neatly as possible it has left an obvious gap that I'd like to 'fill' before applying varnish to make it look a little tidyer...what's the best way to do this??

[CedGTV]

Just sand it with the gap there and add some of the flour/dust that you will make during the sanding and screening to some PVA and fill the gaps after sanding but before staining/varnishing.

If the gaps are larger then back up them up with a little hardboard/thin ply under the edge of the board to give the mixture above something to lay to.

[Laurel Green]

Either with wood filler that matches the floor colour or, save the sawdust from the sanding machine and mix with glue

ETA: Didn't see the above post.

[singlecoil]

If you use the sawdust, it should go a bit darker when the glue is added, which is good. Filler which is slightly darker is always better than a filler that is slightly lighter.