It think the idea is something you can do quickly, as if you 'just take it from your hip pocket'.

In Arabic we say, for example:

السؤال جيد، ولكن الإجابة صعبة، لا تتوقع أن أضع يدي في جيبي لأجد الإجابة لك

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Initi~ discussion or brainstorming activities that you deliver to address this concept will also give you a quick assessment (sometimes referred to as a hip pocket needs assessment) of the participants level of knowledge around health promotion.