"Tool the joint" refers to running your finger or a similarly shaped tool around the edge of the piece after it's in place, to smooth the sealant that has pushed out from under the piece. It really applies to mounting glass or plexi inside a frame that wraps the edge 90 degrees. If you're sealing a plastic window to a mostly flat surface as you would on a Catalina, the sealing takes place in the area where the larger glass overlaps the smaller port cut-out. There's not much area to tool, only the thickness of the glass that is used. I've always been of the school that you work like heck to avoid having to tool sealant -it can make a heck of a mess, and only affects the very outer-most edge of the joint. I prefer applying pressure to the joint with weights, clamps, or even tape in some cases. Leave the joint unmolested for 24 hours. If you did your prep work correctly and applied the correct amount of the right type of sealant, you should be good to go.
Be careful about screwing through lexan or plexiglas. For starters, you must purchase special drill bits. Hardware store bits are for steel and have the wrong angle at the cutting surface. You'll crack nearly every hole if you try to drill with those. Second problem is expansion and sealing of the hole. Because these plastics expand and contract a great deal with changes in heat, the holes must be much bigger than the screw that goes through them, and the screw cannot be tightened against the plastic. If it is, the plastic cannot slide under the screw head during expansion/contraction. If the holes are not big enough, the plastic will crack when it hits the screw and still needs to expand more. Catalina found this out after using screws for a few years, they no longer use them. Next problem is how do you prevent water from getting around the screw head and through the enlarged hole? It becomes a real song and dance to put nylon or rubber washers under the screw heads, then try to tighten them enough to seal out water -yet allow the plexi to move underneath.
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