Real simple chord structure for'Boom Shacka Lacka'taken from UB40`s 2009'Labour Of Love IV':
(*below i`ll Tab the main Sax Riff for use if wanted?)

G=EADGBE  D=EADGBE
  355433    x57775
       
Intro||:G  |G  |D  |D  |G  |G  |D  |D  :||

Verse 1:
G                         D
Come on and gather `round children,
G                               D
Lets get together and sing this song,
G                  D
Got to settle down children,
G                          D
Lets all join in sing this song,Sing it,Sing it.

Chorus 1:
G                       D
Boom shacka lacka lacka,Boom boom boom,
G                       D
Boom shacka lacka lacka,Boom boom boom,
G                       D
Boom shacka lacka lacka,Boom boom boom,
G                       D
Boom shacka lacka lacka,Boom boom boom.

Verse 2:
G                             D         
I`d like to take this time to thank you all,
G                                 D
Thank you from the soul deep in my heart,
G                     D
Thank you for the love that`s going around,
G                      D
We give it to you with some sweet sound.

Instrumental:G  |G  |D  |D  |G  |G  |D  |D  |

Chorus 2:
G                       D
Boom shacka lacka lacka,Boom boom boom,
G                       D
Boom shacka lacka lacka,Boom boom boom.

Saxaphone Middle:G  |G  |D  |D  |G  |G  |D  |(rest)  |

Verse 3:
               D
Dance a little children,
G                 D
While i sing this song,
G                 D
Jump a little bit higher,
G                 D
While i sing this song,Sing it,Sing it.

Chorus 3:
G                       D
Boom shacka lacka lacka,Boom boom boom,
G                       D
Boom shacka lacka lacka,Boom boom boom,
G                       D
Boom shacka lacka lacka,Boom boom boom,
G                       D
Boom shacka lacka lacka,Boom boom boom.

Instrumental:G  |G  |D  |D  |G  |G  |D  |D  |

Chorus 4:
G                       D
Boom shacka lacka lacka,Boom boom boom,
G                       D
Boom shacka lacka lacka,Boom boom boom,
G                       D
Boom shacka lacka lacka,Boom boom boom,
G                       (rest)
Boom shacka lacka lacka,Boom boom boom.

Outro||:G  |G  |D  |D  |G  |G  |D  |D  :||

(*Main Sax Riff to make it a little more interesting than two Chords).

E||:------------------:||
B||:------------------:||
G||:---4h5-7--4-5p4---:||
D||:-5--------------7-:||
A||:------------------:||
E||:------------------:||