It works well on two levels for the children as:
1) they get the proceeds of the sale and
2) they get a pocket money raise because the parents feel guilty for not giving them enough pocket money in the first place
Sometimes used to fence stolen car stereos in the more dungeoneous povo estates
Father: Oh God, I think the kids have just had a garage sale. I swear I saw Mrs Fisk from number 18 walking home with a smile on her face.
This term makes more sense applied to canoing where there are boatloads of gear than in skiing where the gear strewn is limited to skiis, poles, and maybe a hat.