Whats this for?

[DerektheSecond]

On the offside of my caravan at the front I have two white plastic squares approx 2"x3" one near the top and one about halfway down.In the middle of the squares there is a horizontal "bar" which sticks out about 1/4" from the side, any idea what these are for?

Thanks

 

[SBS]

Multi mast plates?

http://www.gradeuk.co.uk/store/shelf.asp?shelfid=58S61S1
Mike

 

[DerektheSecond]

its a Uni-Plate is this for an ariel?