Dapol electric signals

[7000Britannia]

Hi guys,
running 00, just completely rebuilt my layout and looking to adding working signals,
looking at Dapol and needing advice, some website don't have the information I need,
why do some Dapol signals have a box at the bottom and others don't, this may seem like a silly question but I get confused very easily at my age, (retirement was a long time ago), I am adding two pictures, not necessarily what I am after, just to show what I mean,
all help and advice appreciated

[GeraldH]

I think the box is just a representation of the baseboard, but they could have made it a bit clearer. I don't have any myself so perhaps someone else has better information?

[7000Britannia]

thank you Gerald H, much appreciated,
I love planning and building my railway, run it for about 3 months, strip it down and start again so scenery not a big thing,
have told the wife this is my last build, she laughed????, saying that I have already altered it twice since I "finished" it 3 weeks ago,
so scenery staring to be added hence electric signals instead of having to lean over and push a lever at those that clip in the track

[7000Britannia]

finally found information on the box - https://www.youtube.com/watch?v=37_FNy7L4uA - bit long, 26 mins 45 secs