Green’s Dictionary of Slang

flange n.

[SE flange, that which stands out from the surface, esp. a collar]

1. the head of the penis.

[US]Trimble 5000 Adult Sex Words and Phrases.
[UK]B.S. Johnson All Bull 66: Walk flange in flange with me, / You are my destiny.

2. (orig. US) the vagina.

[US]Alt. Eng. Dict. 🌐 flange (noun, slang) Vagina.
[UK]Roger’s Profanisaurus 3 in Viz 98 Oct. 13: flange 1. n. fish mitten. 2. n. coll. a group of baboons. 3. n. coll. Fanny; blart; tush.
[UK]P. Baker Fabulosa 292/1: flange 1. a vagina.
[UK]R. Milward Man-Eating Typewriter 32: ‘[W]e were raped repeatedly, oyster, flange, ripped dish’.