You can't use item while looking at fence

While looking at a fence you can not...

• Eat food

• Defend (with sword)

• Throw potion

• Drink potion

• Shoot arrow

• Throw snowball

• Throw egg

• Place entities? (boats, minecarts)

• Read books

• Throw Bottle o' Enchanting
  Etc.

This is probably due to the lead system