article from Interlux website
Traditionally, gratings were made to let light and air into a boat. They may also be used in the bottom of a shower, or in a cockpit, and they can be incorporated into decorative accents for your boat.
Your first step is to mark out the grating. Figure 1 shows a square grating intended to fit in the bottom of a sailboat cockpit or a shower stall. This grating will be 3 feet long and 2 feet wide overall. The edge trim will be 3 inches wide, which leaves an interior area of 2 feet 6 inches by 1 foot 6 inches. As the figure shows you will require 8 slats each about 1 inch wide and slightly more than 2 feet 8 inches long to go across the longest direction, and 17 slats each 1 inch wide and 1 foot 8 inches long to go across the shortest direction. You can buy the slats pre-made at some marine hardware chains or you can make them yourself.
To make them yourself you will need a table saw. Because the slats in the longitudinal direction will be fastened to the underside of the grating, the ends will be cut slightly differently to the transverse slats (see Figure 3). This may change the slat width or the open space between the slats slightly and should be carefully figured.
When you select your wood pick a piece with the grain running along the wood. If the grain runs diagonally across the wood, the grating will probably snap when any strain is put on it. Select the widest panel that you can find in the desired thickness.
If you want to make one-inch wide slats you can start with two pieces of wood with a suitable grain about 8 or 10 inches wide. One piece should be about two inches longer than the longest direction (about 2 feet 8 inches) and the other piece should be about 2 inches wider than the crosswise direction or about 1 foot 8 inches.
To make the slats, mark out 1-inch intervals across the wood. Using a router cut out every alternate slot to half the depth of the wood, as shown in Figure 2. Now run the wood through a table saw to cut each slat. The saw blade thickness will take a small amount of wood away from each slat, so you may have to adjust your slat thickness slightly to allow for the saw blade. Repeat the process for the other piece of wood to make the slats going in the other direction.
If you are using wood that is likely to split you may find that pieces of wood break off the slat. In that case, cut the wood into strips first and clamp them together to rout out half the thickness.
Assemble your grating as shown in Figure 3. Do not epoxy it together yet. When it is completely assembled, take each slat out and mix a batch of Epiglass Epoxy Resin. Apply the Epiglass Epoxy Resin to the inside faces of each joint, taking care not to apply too much. Set the slats in place. Before the epoxy sets check the entire grid for squareness.
Now you will need to make the edge pieces of the grating, These can be made with corner lap joints, miters, or mortise and tenon joints. I prefer to use a mitered joint with a biscuit in each corner because it hides the end grain. If you do not have a biscuit router, a mortise and tenon joint, as shown in Figure 4A, is stronger than the lap joint shown in Figure 4b.
The inside face of the assembly will need to have slots cut to hold the ends of the slats. These should be made on the underside of the grating and can be done in two ways. The first is to chisel out each individual slot and make the ends of the slats fit. The second method is to rout out a groove around the edge of the assembly and fasten the slats into it, as Figure 4 shows. If you wish, you can add filler pieces to fill the space between the slats, but because the groove is on the underside of the grating it is unlikely to be noticed.
Making a Coffee or Cockpit Table
Having made the basic grating, you can easily build it into furniture. Figure 5 shows how a coffee table can be made with a grating top. The only additional parts you will need to make are the legs and the cross piece to hold the legs together. Note that the top is secured by locating it on vertical dowels set into the top section of the supports. Taking out the pegs, securing the legs, and popping the top off the dowels, can disassemble the table. For use in the home this is acceptable, but for use on a boat, where the table might slide around, it should be glued or screwed together. You can also make a chair or bench with a grating for a seat, or use a small grating as an accent in other furniture.
A Cabin Sole or Locker Bottom Grating
A grating in the cabin sole provides a highlight that can hide a dustpan or a drain for wet clothes. To install a grating into the cabin sole or a locker bottom, determine the size of the grating and make it to suit. Then cut the hole in the cabin sole or remove the old locker bottom. Note that you will have to add supports under the cabin sole to hold the grating as well as gluing it into the sole. These supports can also be back screwed to the bottom of the sole boards.
Gratings, then, can be functional items that provide highlights for cockpit, cabin, or shower soles, or they can be used as accents in furniture to make it more interesting and nautical.
Original article from Interlux website