Mechanical Pencil

1. Lead Holder

1.1. Multiple lead tubes

1.2. Single tube with lead

1.3. No tube; lead holder

2. Lead Pusher

2.1. 3 separate pushers

2.2. Single adjustable pusher

2.3. 3 inline pushers

2.4. No pusher

3. Shape of Pencil

3.1. Triangle

3.2. Circular

4. Length of Pencil

4.1. Short

4.2. Medium

4.3. Long

5. Eraser

5.1. Twist-out

5.2. Static

5.3. None

6. Refill Method

6.1. Disassemble to insert lead

6.2. Put lead through tip

6.3. Refill through eraser hole