Take an aluminium baking tray and cut it into rectangles. (Available from any baking supply shop). Cut it oversized, as you can trim it to size later on.
This is how I make 1/24th scale corrugated roof sheets.
For information: roof sheets come in various sizes, with standard lengths being 2.4m, 3m and 3.6m, and having widths of 660mm and 990mm. However, these sizes can vary depending on the roof style, so you will have to determine that by yourself.
The Sheet Material
To make the jig parts, start by cutting two pieces of wood, with one being roughly half the length of the other, with the longer one being longer than the length of a standard toothpick.
The jig dimensions can vary, but I use 5mm thick, with a width of 20mm.
Now glue toothpicks to these pieces of wood, and be sure to have a toothpick-thickness spacing between each.
Next, squarely cut the tips off 20 toothpicks and glue these (length to length) to a longer, wider piece of wood as explained above. The length and width would be determined by the required scale width of the scaled sheet you are making. (I suggest making it MUCH bigger, so that you don’t have to remake the jig the next time you need to make a longer/wider sheet.
You now have 3 jig parts. Let’s refer them as a small jig part, a medium jig part, and a base jig part.
The Jig
The size of the jig will depend on the size of the scale sheets that you want to make.
The jig consists of two parts: A top and a bottom part.At 1/24th scale, standard size toothpicks will be used as they give a relatively accurate corrugation.
The Method
Placing the aluminium sheet squarely on top of the base jig part, and starting from the left (if are right-handed) edge, press down with the small jig part, and move it along the length of the sheet. This will impress the shape into the sheet.
Now repeat the sliding/shaping action, but using the medium jig part.
Now you try…
Once the corrugated grooves have been established, positioning the small jig part in the last groove on the right, and slide it again as before, thereby making a second set of corrugations.
Lastly, use the medium jig part to deepen the corrugations.
Repeat the process until complete and cut the sheets to size using a normal scissors. Straighten any dents by putting the (now corrugated) sheet back in the jig and refreshing the grooves.