Fender Bass aficionados

It's called a tug bar. You anchor your fingers there and pluck with your thumb.

 

Pictures in-use available here.

 

Flip the bass over, you may find the hootenanny strap button. It was just as useful.

 

I sometimes use my thumb , they're handy . That gets your thumb right over the end of the fingerboard , you can get a quasi upright sound around there . Handy for swing or jump blues .

 

There was also a chrome cover over the pickup, so Leo's idea was lay your palm on the cover and anchor your fingers on the tugbar, and pluck the string with your thumb. The bridge cover also had a mute under it.
Remember, he was trying to make an electric instrument sound like an upright

 

Rutger Gunnarson, bassist for ABBA found it very useful
{they actually work well with the narrow Fender style strap}

 

I thought it would be fun to try to learn to use mine. But it wasn't fun, it was funny. But I left it on for the sake of keeping the bass intact. I can play with my thumb but not using the tug bar.

 

Great post, but - is there something wrong with my eyes? I can almost swear that he's not using it at the 0:57 mark, but later in the video - it looks like he is. If so, I wonder why the change for different takes.

 

No change...what you were seeing was the shadow of the strap - from the stage lights - on his shoulder

 

Thanks! The shadow totally fooled me.

 

FWIW, all that schmutz on the pickup has a FUNKtional purpose.