Now, that both sides of the deck are covered in fiberglass, the hatches or lids can be cut out. I like to build flush hatches for several reasons:

• They look good
• It is less labor-intensive
• Water has no chance of prying the lid off
• Little deck spray
• Simple watertight seal
  
  The pattern from the plans is aligned and taped to the deck centerline and its contour is transferred.
  Both the front and rear hatch contours are on the same piece of paper. Use the pattern to do the large hatch first before it is trimmed.

Finally, as the cut passes through its half point it helps to hold the hatch lid in place with some duct tape. This reduces vibration and chances of the narrowing neck breaking off prematurely.

It is important to use a new sharp saw blade so that the fiberglass doesn't get snagged and ripped off the wood.