The blanks in the clues below can be filled in with the same two letters, in the same order, to form words.

1. _ _ H
2. H _ _
3. BI _ _
4. C _ _ H
5. D _ I _

HINT:
The two letters form a word in themselves.

Answers:

The two letters are AS.

ASH/HAS/BIAS/CASH/DAIS