MATERIALS

Some of the products and methods below are recommendations only. There are endless variations on this theme. The specific product and supplier recommendations below are the best.  The method described below is proven, and has resulted in shields lasting a decade of use with minimal repair. 

Core: 
1 sheet 1/2" good interior grade plywood available at Home Depot. Avoid warped or excessively knotted plywood. (It's really 5/8", they just call it half inch.)  If you can get it and you know what you're doing, the plastic curved scutum is the way to go. (Not recommended for beginners, though!) To size the core, take 3" off left, right, and top and bottom of the FINAL shield size you want (for a rectangle tower shield). 2' by 4' sheets from Home depot will allow for up to a 2.5' (30") wide by 4.5' (54") shield. Your finished shield should cover you from your throat to your knees. 

Use a file or a sander to smooth the edges of the wood core--just a little, to *just barely* round the edges and remove the sharpness and any burrs from the cutting.

Forearm strap and hand Grip. (Yes, historic Romans used punch shields. I don't recommend it for Dagorhir combat.) 
Use thick leather (or some *proven* man-made substance) of at least 2" wide and 3/16" thick for the forearm strap. 
Use a Home Depot cabinet handle for the hand grip. 
Get nuts, bolts, and washers and lock washers for the strap and grip.  

Open Cell: 
2 sheets of the 2" thick 24" x 48" Unifoam (McMaster-Carr part 85735K56 for $23.95 (This will be enough for even a very large shield. You'll have extra for javelins. If you can find 1.75" or 1.5" thickness, that will work too. Occasionally Rome buys a large stock for a significantly lower cost. But we have none at present.) 

Closed Cell:
1 sheet of 3/8" thick EVAlite (McMaster-Carr part 86095K23, for $20.46
1/2 sheet of 1/2" EVAlite (McMaster-Carr part 86095K24, for $23.83
You can substitute EVAlite for a regular 3/8" camping pad with decent results and a significant savings. But I recommend the EVAlite for longevity. And for swords. 

Adhesive:
1 can of 3-M "77" (multi-purpose) spray adhesive (or perhaps 2 cans for 3 shields; about $10 each at Home Depot)

Blades:
LOTS of fresh "standard" exacto knife blades for cutting EVAlite
1  2" long foam-cutting knife blade per shield to cut the Unifoam 

Cutting the thick foam neatly *requires* a really long and sharp blade and is the trickiest part of making one of my shields.  Fortunately, rectangle shields are all straight cuts. 

Tape:
1/2 roll of 3M duct tape 

Miscellaneous:
1 Metal yard stick for measuring and cutting. 

Cut a piece of plywood into the desired shape, rounding all corners to eliminate the danger of sharp edges. 

The first thing you should do after you measure and mark where you want to put the strap/handle. Glue closed cell on the shield backing, as seen in the far right graphic. This will act as a buffer between the board and your arm to absorb impacts and reduce the chance of injury to yourself.  

Do this BEFORE you drill and strap the shield. Use washers! MEASURE TWICE, drill once and strap once.

 

Drill holes for your arm straps above the center of your board; one for your grip and one for your arm just below your elbow.

Cut your straps to the necessary lengths and bolt them to your shield. Make certain the bolt excess faces your side of the shield. For the hand, I recommend a durable door handle that fits your hand comfortably.

Next, glue closed cell foam around back edges, front, and then the edges of your shield as in the diagram. Putting foam on the front and back first will provide a larger surface area for your edges, giving you more surface area to adhere to. Following this, glue open cell "computer packing foam" to the front of your shield, making sure the piece you apply is cut to the precise dimensions of your shield face. Apply computer packing foam to your edges, and finally apply strips of closed cell to the outside edges to ensure progressive resistance. Reinforce your shield padding's structural integrity by applying strips of duct tape to every glued seam.

Once you have done this, get some durable red cloth (canvas is best) and secure it snugly over the entire surface and edges of the shield, stapling it on the inside, or your side. Paint Rome's shield logo on the front in gold or yellow.

-Dominus

Special thanks to Mark (Guntar von Keitz) Gibson for his design, and for the graphic above.