Gaps in bed

[Bigdogg]

Hello everyone,

Picked up my 24 F250 in January. 
I have noticed that there are gaps between the bed and the sidewalls. 
Not sure why??..??… Maybe someone who knows more about the design why this is 

 

I purchased the hard folding Ford Tonneau cover to keep water and debris out of the bed, but the gaps in the bed allow dust from the gravel roads to come up into the dead and cover everything in the bed with dust. 
Very Frustrating. 
 

Any suggestions on what to seal those gaps with to prevent dust intrusion????

 

thanks for all your help. 
 

Bigdogg