Window frames joined with sill

[Small]

How do I fill a gap between the bottom of a wooden sash window frame and a concrete (possibly, it's hard) (exterior) window ledge. I was going to use Wood filler but the gap goes back a fair way and there is moss and loose debris under there.
If I use wood filler - I would need a hell of a lot of it to fill the gap and does wood filler bond wood to the concrete window ledge effectively? Any help appreciated. Cheers.

[stevenc1603]

I would recommend not using wood filler. That is used for filling holes and the like in wood, and not for gap filling.

What you are needing is an exterior sealer or filler. Have a look in the silicon section of your DIY shop for such items.