Criteria define success; constraints limit resources; preferences say what we like. Reused paper is one sustainability check, not proof of the best environmental choice overall. Safety: Use only light pencils and paper; no sharp cutting or tipped furniture. Stop: End after checking one model. No added tape, heavier loads or sharp tools.

Materials: Two reused paper sheets, pencil and ruler; One wooden pencil to hold; stable flat work surface 1. Set a pencil-holder problem. Agree these criteria: retains one pencil during the local slide defined in step 4; fits within 15 cm by 15 cm; uses reused paper; unfolds without tearing. Add a personal preference separately. Read the complete test method before rating either proposal. 2. Sketch two ideas: A, a paper channel with two long edges folded up; B, a paper sleeve made by folding the sheet around the pencil without fastening it. Make a comparison table Idea | Holds | Fits | Reused | Unfolds | Preference. 3. Judge each idea likely yes, likely no or uncertain for every criterion. Use the same available paper and no tape. Pick one to build, giving a reason based on the table. 4. Build the chosen idea and measure its footprint. Put the pencil in it. Mark start and end lines 1 cm apart beside the paper edge. Hold only the paper base. Slide that edge between the lines during a slow count of three, without lifting. Record whether the pencil stays inside: yes, no or unclear. Unfold the paper to check the final criterion. 5. Compare predicted ratings with the finished model’s results. State what you like, whether it met each criterion and one change that could improve function or material use. Label the proposed change not yet tested. Done: Two ideas are rated against all criteria; one built model is checked and one improvement proposed. Proof: Keep both tables and the sketches. Note adult folding, measuring or suggested ratings. Stop: End after checking one model. No added tape, heavier loads or sharp tools.