Sealed in their foreheads

At work I'm listening to the audiobook "Prophecies" by Matthew B. Brown. He talks about Revelation 7:3 which reads:

"Saying, Hurt not the earth, neither the sea, nor the trees, till we have sealed the servants of our God in their foreheads."

He quotes a statement by Joseph Smith which explains what it means for someone to be sealed in their forehead:

“SEALING OF THE SERVANTS OF GOD.—August 13, 1843. "Four destroying angels holding power over the four quarters of the earth until the servants of God are sealed in their foreheads, which signifies sealing the blessing upon their heads, meaning the everlasting covenant, thereby making their calling and election sure. When a seal is put upon the father and mother, it secures their posterity, so that they cannot be lost, but will be saved by virtue of the covenant of their father and mother."

It means that those servants will have their calling and election made sure by the laying on of hands.

Chapter 7 then goes on to mention that there will be 144,000 of these servants who will have this privilege. The Israelites, to give a number a superlative quality, squared it, hence 12 tribes, 12x12=144. to exaggerate it further they multiplied it by 1000. John's audience would not have taken this number literally. They would have understood it to be describing a fullness of individuals taken from each of the twelve tribes who will enjoy the privilege of having their calling and election made sure and who will serve the Lord in the last days. Verse 9 describes these people as being: "a great multitude, which no man could number".

Update - 1/16/11 - This sealing in the forehead refers to the gold plate bearing the inscription כדש יהוה (Holy to Jehovah) which was attached to the mitre which the high priest wore. This plate was located just above the forehead.