How do فَتْحٌ and مِفْتَاحٌ differ?

Ism al-Ālah: Definition, Three Patterns, Paradigms and Formation

• Both are active participles
• Fatḥ is a verbal noun and miftāḥ an instrument
• Both are imperatives
• Fatḥ is the instrument and miftāḥ the verbal noun