You will notice a bracing bar on the top and middle of the box (NOT the hanging bar), there is another at the bottom (see the pine wood strips, the middle one being the most obvious). The top and bottom ones were really great to pull the box together as without these the lid and floor would have bowed a bit. I mostly used panel pins to nail it together but used screws on the sections with the bracing to really secure the box.
As you can see from the pictures below its fairly sizable. You could achieve similar (large or small) by buying a cheap cabinet from a pine furniture store or somewhere like Ikea.
The design of this box is based on air flow, regardless of the fact you see globes, and you will notice that there are no massive holes to achieve this, making huge holes creates a challenge to find a suitable fly filter and you will probably find that the air flow isn't great. Holes can always be made bigger later!
I based the size of the side holes on the cabinet air vent I could source (Caravan supplier on eBay for ventilated cabinet fitting). To make the holes the best option is a hole saw used on a drill. I made the side holes roughly in the area aligned either side of center of the hanging meat. This will create airflow across the meat which is what dries it!
On the roof I looked at using a 220v (US is 110v) fan but the cost was high as these were sunbed fans. So instead I opted for a 12v fan used for computer cooling. I sourced this from China on eBay again as well as the really cool filter covers. This fan is a 120mm PC case fan and cover (Hole saw this size is expensive so if you have a jigsaw it may be best or see if a mate has one).
You will see the 12v transformer, the same ones you use for down lighting etc. These components are much cheaper than the 220v ones I looked at and buying two would not be a bad thing for spares!
These shots show a close up of the vents (about 80mm in size) and placement. I also used the cut outs from the vent holes as the brace for the dowel rod to hold the Biltong, you can quite easily just attach using a screw or bracket. When the door is closed and the Biltong maker on you should have a decent enough airflow to hold a small piece of paper or plastic onto the vent hole on the outside. Note the fan blows OUT the Biltong box NOT IN!
Lastly you will see I do use lights, for me this has some advantages but not essential to the drying of the Biltong, unless you have a humid climate then its essential. Firstly I can see what I am doing when working in the Biltong box in the dark garage. Secondly the heat from these 100W globes (60W works or halogens) does take the cold edge off during winter, don't need the meat freezing! Lastly it does dry the Biltong closest to the lights a wee bit faster so I tend to move the meat around depending on the drying rate and bring wetter pieces closer to the lights or vents, depending where you seeing the best Biltong drying results.
I tend to check on a 12 hourly cycle after the first 24 hours, morning and night basically, and move pieces as necessary. Sometimes you can also turn the meat around if you need the wetter top part to dry, the hooks pass through the Biltong fairly easily. Speaking of which I simply used plastic coated garden wire but ideally stainless hooks are best.
The lights have a really snazzy cover made from beer cans, what more can I say.... This can be made from tin or beer cans. Just take care when cutting and bending the sharp edges and even latex gloves will help keep any cuts at bay. If you attempt this just do it slowly and carefully.
I was really lucky and got a sheet of aluminium that I used to create a drip tray. Alternatives to a drip tray include using epoxy based paints or sealer that can be applied to create a waterproof base (CHECK with the hardware store on suitability\toxicity for this application). Last thing you want is drippings all over your Biltong box, unsightly and probably not too healthy.
This Biltong box could also be adapted as a dual purpose cold smoker. Just watch your fan as smoke particles are smaller than dust and get right into your fan mechanism. Avoid using the fan during smoking but also consider making it easy to remove as the hole in the top will make a nice chimney. Caster wheels on the Biltong box (size dependent) really help too for easy one person moving of the Biltong box.