I've always wanted to create a convertible briefcase/backpack and just wasn't sure about how exactly to construct it. I did some brainstorming and came up with this idea. It's a basic briefcase that has a removable strap that doubles as your shoulder straps when reconfigured as a backpack. As far as dimensions and stuff go I just laid it out on a big sheet of paper and just started building.

Step 1: Tools/Material

I have quite a few leather tools that I've procured (mostly from Tandy Leather Factory) over the years. The tools shown aren't all that I have but are the most used (Forgot my strap cutter). You can get by in the beginning with just some basic tools such as a utility knife, straight edge, makeshift awl, stitching needles. But as you expand in your leather working you'll definitely want to get more tools. This will greatly improve the fun and quality of your work. You'll also need sponges and rags for dyeing. A cutting surface is essential. I have 4 plastic kitchen cutting boards screwed to my worktop for cutting. Get a couple books to look through too. The ones shown are my favorites ( available here )

I also use a Dremel with a flexible shaft that I've had for some 14 years. These come in handy for tough leather if you have a hard time getting your stitching awl through. Just pop a 1/16" drill bit in and you're all set. You can also use it with a small sanding drum to even out glued up edges such as at the gussets or on the handle.

Material

8 oz. Leather

leather dye

leather finish

3- 1" buckles

6- 1" Dees

1- 1 1/4" Dee

2 Swivel snaps (to attach shoulder strap to bag

Rivets

Thread (I use super thick waxed synthetic)

Step 2: Design

I did some sketches on paper and then I did somewhat of a scale drawing. I then transfered all those dimensions to a large sheet of paper and used that for my pattern. I'll later transfer that to a piece of grey board as a permanent pattern.

The main body measures 15" x 34 3/4"

The side gussets measure 4 3/4" x 10 1/2" along sewn edge. I added another 2" for the flap so stuff won't fall out if laid on its back.

The placement of the buckles, handle, and billets were located as I built it. You'll see in further steps. I'll do it this way when developing a new bag because I like to mess around with the placement of the different design elements as I go.

Step 3: Cut It Out! and Burnish

Once you have your pattern figured out cut out all your pieces. I didn't have an exact dimension on the main body piece but would figure it out as I went. I made the bag basically out of 3 main pieces: 1 the Body (wraps around from front to back to the flap) and 2 gussets (side pieces).

I like to cut out all the pieces that I can right away and burnish all exposed edges that won't be doubled up like where the gusset and body are joined. Or burnish all edges that will be difficult to do later.

Typically I dye my leather before this step but I was trying something new this time...and found out that I don't like doing it this way.

Step 4: Form the Gussets

Use a v gouge to cut a groove about a third of the way through the flesh side of the leather where your gusset needs to bend. It's about 3/8" in from the edge. Then thoroughly wet the leather. A cellulose sponge is great for this. Once saturated bend and tap with a smooth faced hammer and then smooth the leather with a bone folder or a smooth piece of plastic.

Step 5: Fit Gusset

Here I used office binder clips to temporarily hold the bag together as i located the handle in the center of the top and to mark where the flap would meet the front. Mark it lightly with a scratch awl. You can then transfer these marks to your pattern to be able to make the same bag again.

Step 6: Make Your Handle

This is a pretty simple handle. Just cut a strip of heavy leather 1" wide and 16 1/2" long then fold it twice. Slip on two 1" Dees and then cement and stitch. Burnish edges.

Attach a strip about 1 1/2" wide to body of bag as shown in pics to attach the handle. Make sure to stitch and rivet the center section first and then slip your handle on and finish stitching.

Step 7: Add Dees and

Two 1" dees are used for the handle in previous step

Two 1" dees are used on the back towards the bottom outside edge. These will be the position of the straps when used as a backpack. These are put into a small strap that is stitched in between the body and the bottom protectors.

Two 1" dees are used on the side gussets for the strap to attach to when used as a briefcase.

These can all be attached before the gussets are cemented in place.

Attach one 1 1/4" Dee to the back in the center towards the top. This will be used when the bag is converted in to a backpack.

Step 8: Add Your Straps and the Buckles

I know I keep using the same image but I didn't take a pic for every process. Here though you can start to attach your straps for the buckle closures. You can just run them long and then trim them to length once you have the gussets stitched. Add the small straps with the buckles also.

Step 9: Glue Up the Gussets

Cement the gussets on to the main body of the bag.

Step 10: Stitch and Finish Edges

Saddle stitch the gussets to the main body and then finish the edges. Even them up as shown in the pics and then burnish.

Step 11: Make Strap

Make a 1" strap with a strap cutter or a straight edge. make 2 shoulder pads about 2 1/2" x 6 or 7". Use an oblong punch to cut out slots for the strap to fit through. Finish the strap and then add the hardware

Attach it to bag and use...

Now their are two ways to use this bag; As a briefcase or as a 2 shoulder backpack. To convert the briefcase to a backpack you need to undo the swivel snaps from the gusset dees and attach them to the dees on the lower back side of the bag. Then undo the buckle for the strap and run it through the center Dee on the back.

Presto chango!