Related Clues:

• Refine, as a skill
• Work on perfecting
• Perfect, as skills
• Sharpen, as a knife edge
• Sharpen, like a skill
• Sharpen (with a whetstone)
• Fine-tune over time
• Perfect gradually
• Sharpen, like skills
• Sharpen, as an axe
• Put an edge on a blade
• Sharpen, as a sword's edge
• Take a strop to