How Do You Tighten These?

[Mike K]

I have several of these holding down both windscreens ... there is easy access to the bolt heads underneath ... but how do you keep the round top from spinning when you tighten the
bolt from below?

 

[02HoWaRd26]

Not the exact ones however I’ve seen a very similar design.
The ones i say the end of the bolt side, had a small hex tip you hold with a wrench then use a wrench on the nut. It could even be an allen in the top of the bolt tip.

 

[Terminal Velocity]

Guessing it's a cap to cover the bolt/screw to give it a finished look. No idea how to properly pop it off.

 

[Badchoices03]

Channel locks with something to protect the boat and fastener would be my fix

 

[Havasu blue label]

Mexican wrench vise grip

 

[$hot]

Is there an Allen key in the base of the bolt?

 

[BDMar]

Typically there would be a nut (not a lock nut), lock washer, and flat washer. A thumb pressed on top of the silver head should keep it from spinning. I've used a cordless 1/4" impact to get them snug then finish by hand so not to crack the windshield

 

[Mike K]

maybe it’s just a cap ... hopefully ... I didn’t think about that ... that makes sense. I’ll check when I get back out there ... I could ask Rusty () he built the boat in 2009 .... nah !

 

[530RL]

Looks like a decorative cap to me?

 

[MK1MOD0]

Channel locks with plastic jaws to pull the cap?

 

[Mike K]

I just spoke with the original owner ... awesome guy ... he told me he used “soft jaw” pliers to grip the top while someone below turned the bolt. Problem solved. Thanks for everyone help.