1) A large net placed between trees to entrap deer.
The first OED reference is from the Act of 1503 which was an attempt to deal with the problem of poaching: the greatest destruction of red deer and fallow within this realm in time past hath been, and yet is, with nets called deer-hays and buckstalls. An arrest in the Forest of Pickering confirms how big a problem such forays were and provides an earlier reference to the word in this sense: 1489 Thomas Thomson … cum aliis personis ignotis Riotosis … in media nocte … cum uno equo onerato cum retibus vocatis bukstalles et Ropes. Previous explanations of the term have concentrated on the use made of buckstalls by poachers but in the Coucher Book for the Forest of Pickering it is employed much earlier in a different context. In 1336, the Prior of Malton asserted his entitlement to certain liberties in the Forest, claiming that he and his men should be quieti de bukstallis, tristis, etc. This was explained by the editor as a custom which compelled forest tenants to make an enclosure into which the deer were driven, presumably using nets of the kind described. It would not be long before tenants saw how they might turn customary practice to their advantage. Etymology and meaning are more closely knit in the earlier usage.