Whatever it is...I love the stuff!  More than 30 years ago I decided to put a 14" square roofvent in my TinTop Vanagon....I love ventilation.  The kit for the roofvent came with some of that stuff.  Now, after 30 or more years in every condition....the stuff is Bomb-proof!  Never ever a leak, still looks the same after 30 years (meaning...can't see a thing, it's all underneath the flange).
I bet you can go to almost any RV shop and get some of it.  Righto...it is super duper sticky.  And super duper effective.  Good luck at ever trying to remove it though; will take a lot of patience and tools and solvents and elbow grease.

Rich
San Diego

    On Friday, May 1, 2020, 3:59:17 PM PDT, David Beierl <dbeierl@gmail.com> wrote:  
 
 It's variously called mastic, dumdum, Thykol, butyl rubber.  May have
different compositions but what they have in common is non-hardening,
non-shrinking etc.  The "tape" is a bit of a misnomer -- it's just a flat
line of the stuff wrapped on releasing paper.

Yrs,
d

On Fri, May 1, 2020 at 5:33 PM Steven Shelton <shelton4@gmail.com> wrote:

> What is the black sticky stuff around the bolts in the pop-top roof? I
> thought it was butyl rubber but the only butyl rubber I can find is tape.
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