I'm making a bike mount on a 2x6 to put on the floor of the Colorado bed up against the cab. I'm curious what others have for the best way to secure the board down to the bed? There are some small holes in the bottom up there, but not sure what the best way is to fasten this 2x6 down. Any ideas would be greatly appreciated!

 

I believe those are drain holes, might block or plug them up. maybe another solution ? Regards Don