Instructables
Picture of How to Make a Cardboard Clam Hat
This costume was made for a Technology project in my high school.  The task was to make a marine-themed costume out of cardboard for a middle schooler to use at a play or during Halloween.  The costume had to utilize slotted construction and couldn't make use of fasteners and/or adhesives.

Design Brief:
Design and build a marine-themed costume out of recyled cardboard.
Must not use fasteners and/or adhesives and utilizes slotted construction.

Specifications:
-Marine-themed
-Easy assembly
-Slotted construction
-Play or Halloween

Limitations:
-Only recycled cardboard
-Middle school student
-No fasteners and/or adhesives
-As few parts as needed

Supplies List:
Supply          Quantity              Size
cardboard         1                  30''x30''

Tools List:
Tool               Tool Number                   Purpose
Pencil                     T1                Drawing
Utility knife             T2                Cutting cardboard
Cutting board        T3                Protecting surface when cutting
Ruler                       T4                Measuring distances

Parts List:
Part                    Part Number          Quantity
Lower shell                P1                         1
Upper shell                P2                         1
Connector                  P3                          1
 
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Step 1: Making the Lower Shell

Picture of Making the Lower Shell
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1.    Lie the cutting board (T3) on a flat surface.
2.    Put cardboard (S1) on top of cutting board (T3).
3.    Use pencil (T1) and ruler (T4) to draw a circle with a diameter of 22 cm.
4.    Use utility knife (T2) to cut circle out of the cardboard (S1).
5.    Use pencil (T1) and ruler (T4) to draw a circle with a 22 cm circumference.
6.    Use utility knife (T2) to cut out the circle.
7.    Use utility knife (T2) to cut from sides of lower shell (P1) to bottom.
8.    Cut a 4.5 cm tab in bottom of lower shell (P1) with utility knife (T2).
9.    Make a 1 cm long cut on both sides of the tab with utility knife (T2).
10.  Make an angled 4.5 cm long slot a half centimeter away from the previous cuts with utility knife (T2).
11.  Fold edges if wanted.