Friends:

 How do the 5 Mental Hindrances become 10?

The Blessed Buddha once explained:
How, Bhikkhus, do the five mental hindrances multiply into ten?                
Own internal sense-desire is a hindrance. Another's external sense-desire
is also a hindrance. Sense-desire is thus twofold: Internal and external!
Our own internal ill-will is a hindrance. Other's ill-will is a hindrance too...
Lethargy is a mental hindrance. Any laziness is also a mental hindrance.
Lethargy-and-laziness are therefore a dual mental hindrance.
Restlessness is a mental hindrance. Regret & worry are also hindrances.
Therefore can restlessness-and-regret be explained as two hindrances.
Doubt and uncertainty about any internal condition, are hindrances.
Doubt & uncertainty about an external condition, are hindrances too.
Thus does doubt-and-uncertainty become like a matched mirrored pair...

More on  these 5 Mental Hindrances (Nīvaranas):
http://What-Buddha-Said.net/drops/II/The_5_Mental_Hindrances.htm
http://What-Buddha-Said.net/drops/II/Feeding_the_Hindrances.htm
http://What-Buddha-Said.net/drops/II/Starving_the_Hindrances.htm
http://What-Buddha-Said.net/drops/II/The_Canal.htm
http://What-Buddha-Said.net/drops/II/Naturally_Radiant.htm
http://What-Buddha-Said.net/drops/IV/Suitable_Substitution.htm
http://What-Buddha-Said.net/Canon/Sutta/AN/AN.I.3-4.htm
http://What-Buddha-Said.net/Canon/Sutta/AN/AN.I.3-4c.htm
http://What-Buddha-Said.net/drops/II/The_Fire_of_Sense-Desire.htm
http://What-Buddha-Said.net/drops/II/Colourful_but_Muddy.htm
http://What-Buddha-Said.net/drops/II/Anger_and_Irritation.htm
http://What-Buddha-Said.net/drops/II/Lethargy_and_Laziness.htm
http://What-Buddha-Said.net/drops/II/Restlessness_and_Regret.htm
http://What-Buddha-Said.net/drops/II/Doubt_and_Uncertainty.htm