Green’s Dictionary of Slang

gig n.4

also gige, gigg
[gigger n.1 ]

a door (cf. jig n.3 ).

[UK]A. Smith Lives of Most Notorious Highway-men, etc. (1926) 208: Milling the Gig with a Betty, i.e., Breaking open the Door with an iron-crow.
[UK]New Canting Dict. n.p.: Mill the Gig with your Betty; i.e. Break open the Door with your Instrument.
[UK]Bailey Universal Etym. Eng. Dict. n.p.: Mill the Gig with a Dub, To open the Door with a Pick-lock, or false Key.
[UK]Scoundrel’s Dict. 14: A Door – Gige.
[UK] ‘The Dog and Duck Rig’ in Holloway & Black I (1975) 79: Then tips you the hint at the gig.
[UK]Grose Classical Dict. of the Vulgar Tongue (3rd edn).
[UK]Lex. Balatronicum.
[UK]Lytton Pelham III 292: I’ll close the gig of the crib.
[US]Matsell Vocabulum 37: gig A door. ‘Dub the gig of the casa,’ break open the door of the house.
[Aus]Crowe Aus. Sl. Dict. 32: Gig, a door.

In phrases

strike the gig (v.) (also strike the gygg, ...jigger)

(UK Und.) to open a door.

[UK]C. Hitchin Regulator 19: To strike the Gygg, alias to unlock the Door.
[UK](con. 1710–25) Tyburn Chronicle II in Groom (1999) xxviii: To Strike the Gigg To unlock the Door.
[UK]‘Ducange Anglicus’ Vulgar Tongue 35: To strike the jigger, to pick a lock.
[UK]Hotten Dict. of Modern Sl. etc. 104: Strike the jigger to pick the lock, or break open the door.
[UK]Hotten Dict. of Modern Sl. etc.
[UK]Hotten Sl. Dict.
[UK]Sl. Dict.
[UK]Newcastle Courant 25 Nov. 6/5: She can strike the jigger to regular tradesmen like ourselves while the omee lies in letty and dreams.
[Aus]Argus (Melbourne) 20 Sept. 6/4: He may strike the jigger, or if his specialty be windows then fly the glaze, which means raise it or star the glaze, or milk the glaze which means break it, while going through it back window is described as the back jump, or going the jump .