Put a 3-letter word in the vacant squares so that, together with the word already there, a 6-letter word is formed.

1.

16.

31.

2.

17.

32.

3.

18.

33.

4.

19.

34.

5.

20.

35.

6.

21.

36.

7.

22.

37.

8.

23.

38.

9.

24.

39.

10.

25.

40.

11.

26.

41.

12.

27.

42.

13.

28.

43.

14.

29.

44.

15.

30.

45.

The solutions are here.