It’s the lovable Sentry Turret from the hit PC/Xbox/PS3 game, Portal! Since its original release on my deviantArt page some time ago, I've received a number of requests for help/tutorials with this model, and in the spirit of the Make It Real challenge, I've decided to write up a concise guide to that end.

BACKGROUND
For those curious, this model was designed using several pieces of software, including student versions of 3D Studio Max and AutoCAD for the mesh, GIMP for the model’s skin, and PePaKuRa Designer to “unfold” it into the final template. PLEASE NOTE, you do not actually need any of these programs to assemble the template in this instructable.

DISCLAIMER
While I will do my best to guide you through the assembly, parts of this model can be difficult for beginners; namely the legs, which are the smallest and most intricate part.

WHAT YOU’LL NEED
> The 2-page template (PDF) attached below
> Your preference of cutting implement (i.e. scissors, a pen-knife, etc.)
> Paper (I would recommend 16-20lbs (60-75gsm) paper, i.e. typical copy/printer paper)
> Glue
> Patience, time, and dexterous fingers
> OPTIONAL - PePaKuRa model file (.PDO) attached below *

* Only for those who already know how to use the program PePaKuRa; while it is a very useful tool, I will not be explaining its use in this guide.

Step 1: Getting Started

Once you’ve printed out the PDF template listed on the main page, you’ll need to cutout the pieces (photo #1). You can do this in sections or all at once, whatever your preference. The pieces are not interchangeable, however, so if you choose to do them all at once, be careful not to mix them up.

FOLDING
This step is optional, and my recommendation varies depending on your personal building experience. For beginners, I recommend making all folds; this will help greatly in the assembly. For those of you with a little more building experience, assembling the model unfolded will soften the model's edges, giving it a much smoother and realistic look. For the purposes of this tutorial, all folds have been made.

There are two (2) types of fold lines: mountain lines and valley lines (photo #2). Once folded, your pieces should look like they do in photo #3. Note that both the lines separating the tabs from the rest of the piece should be folded, too.

Step 2: Assembly - Body

For the first portion of the model, you’ll need the four pieces labeled “A”, “B”, “C”, & “D” (highlighted in red in photo #1). Starting with piece “B”, connect the 5 center tabs to their adjacent edges (photo #2). Put a small amount of glue on the white tabs, and attach them to the rear of the edge’s face. NOTE: if you are using liquid glue, be careful not to use too much glue, as it can cause the ink to run.

Pieces “A” and “C” will attach on each side of “B” (photo #3). Connect all tabs to their adjacent faces, save for the one large tab at the bottom of piece “C” (photo #4). Leaving this open will make attaching piece “D” easier.

Closing up the back with piece “D” is a little trickier. As you close up the back, it gets harder and harder to reach the tabs inside. I recommend starting with the top two tabs, and working down both sides evenly. You can slide a paperclip or toothpick through the space you left open at the bottom to help attach the tabs (photo #5).

Step 3: Assembly - Doors

Setting aside the body for now, we'll start on the turret's doors. The eight (8) pieces highlighted in red and blue (photo #1) will form two separate components. Pieces "E", "F", "G", & "H" (in red) will form the left door, and pieces "I", "J", "K", & "L" (in blue) will form the right door.

Starting with the left door, attach the skinny half of piece "H" to the wider half (photo #2). From here, pieces "G", "F", & "E" will attach to "H" just as they are laid out (photo #3). Finishing the door can be tricky in the same way closing the body was in the previous step.

If you have trouble at the end, you can poke a hole in the center of piece "H" to manipulate the tabs using a paperclip. I used the same space to label the door "LEFT" (photo #4) so I wouldn't get them mixed up (though honestly they're basically identical, so you probably wouldn't even notice it if they were backwards). This spot will be covered by the door's arms later, so the hole and/or labeling will be concealed.

Wash, rinse, and repeat for the second door using pieces "I" thru "L" (photo #5).

Step 4: Assembly - Door Arms/Gun Barrels

The eight (8) pieces highlighted in red and blue (photo #1) will form the two arms attaching the doors to the turret's body. Pieces "M", "N", "O", & "P" (in red) will connect the left door, and pieces "Q", "R", "S", & "T" (in blue) will connect the right.

Starting with "Q" thru "T" (the right side), piece "Q" is basically just a flat cube. The one “angled” side will attach to the door, oriented as shown (photo #2).

Piece "R" is even simpler; the only connection that needs to be made will turn it into a loop. You'll notice on one side all the edges are straight, while on the opposite side the edges are not (photo #3). The "straight" end attaches to piece "Q"; center it as best you can. The "crooked" end will attach to the turret's body later on.

The combined “Q” and “R” can now be attached to the “RIGHT” door (photo #4). Notice that this will cover up your labeling (if you chose to label the doors in the previous setp).

"S" and "T" each make a separate silver gun barrel. Starting with "S", attach the single large tab to its opposite end, forming a cylinder. The large circle with the black dot in the center can then be folded down like a lid (photo #5). Repeat for "T".

Both of these will attach to the side of piece "Q", with the barrel with the smaller dot on top (photo #6). There are no exact markings to position the barrels onto "Q", just use your best judgment.

Repeat the above steps for pieces "M" thru "P".

Step 5: Assembly - Legs

The legs are a bit trickier than most other pieces. In the game, the entire body is suspended from one point in the rear; the front legs are connected to this point via looping rods. Since this was impractical to duplicate with paper, the front legs will attach to the front of the body instead. The point of connection for each leg is still small however (especially for the rear leg), so you're really going to want to take your time on these pieces so they come out strong.

There are three separate sets for this step, one set per leg. Pieces "U" & "V" (in red) will form the front left leg, pieces "W" & "X" (in blue) will form the front right leg, and pieces "Y" & "Z" (in green) will form the sole rear leg (photo #1).

Starting with the front left leg, you'll notice piece "U" has three "tendril" like pieces coming off of one side. The tabs here will connect as indicated (photo #2). See the face I drew an "L" on? This will be the point of connection to the body later (and thus be obscured).

The 4th 'tendril' will fold over to attach to the rest of the piece. Closing this piece is actually not bad; if you work your way evenly down each side, you can still get a paperclip underneath to help with those hard-to-reach tabs (photo #3).

Repeat for pieces "W" & "Z", the other two legs' top halves (photo #4).

The bottom halves of the legs ("V", "X", & "Y") are nice and simple; you'll build these the same way you built the gun barrels previously. The long, thin white tab will attach to the opposite face, and the small black square will fold down like a lid onto its adjacent tabs (photo #5). Note: If you end up with a bit of white showing from the long tab, you can color it with a black marker to help hide it.

You should have two identical (and thus interchangeable) short black pieces ("V" & "X") and one long piece ("Y"). To assemble the front legs, take "V" & "X", and grab the previously completed "U" & "W". Use the four white tabs at the end of "V" and "X" to attach the pieces to "U" & "W". Align them to the center of the face as best you can (photo #6). The two pieces for the back leg will attach the same way (photo #7).

Step 6: Assembly - Completion

You're in the home stretch! Give yourself a little pat on the back for having the patience to make it this far.

Gather your completed pieces from the previous steps (photo #1). We'll start by attaching the doors to the body; the little jog along the side of pieces "N" & "R" will attach along one of the fold lines on the body (photo #2). Attach them one at a time, giving them an appropriate amount of time to dry in-between (depending on how heavily you apply the glue). Be careful not to press too hard while attaching them or you'll crush the body (photo #3).

Now for the legs; assuming they've had a bit of time to dry, I would recommend starting with the two front legs, as they have a more definite (and larger) point of connection (photo #4). My left leg got a little squished while attaching it… whoops! I propped the model up on its back to give it a little time to dry and strengthen up (photo #5).

The location of the back leg's connection will be somewhat variable; you'll want to connect it at about the spot shown in photo #6, but you can move it up or down depending on what position will make it stand level. My model’s front legs ended up being a bit more vertical than was originally intended, so I moved the back leg down a good bit. You can try to prop it on its face to allow it time to dry, but I opted to hold it to ensure the back leg didn't shift. And you're done! Thank you for participating in this Aperture Science Enrichment Center activity! <confetti>

A small side note: If, once dry, you're model has trouble standing (or begins to sag over time, it’s only paper after all), you have the option of affixing it to a stand to help ‘force’ its posture. Make (or choose) an appealing surface, and use a drop of glue (hot glue, rubber cement, or what have you) to attach each leg to the surface.