The same two letters, in the same, consecutive order, when properly placed, will change each word into a new one. Can you determine the two letters and the new words?

AN
FAT
CUT
SON
SLAM

Answer:

The letters LO can be added to or inserted into each word to create new ones: 

LOAN
FLOAT
CLOUT
SOLON
SLALOM

Credit: NY Times Crossword - Dec. 2, 2012
Steven E. Atwood
LO AND BEHOLD!