Back chaining is where you train the final behavior first-in this case holding the item in the mouth with the dog sitting in front of the handler. “倒序”就是首先训练最终的行为-在这个例子里就是衔着物品坐在主人面前。
All the tools include principal of the drill tools, overshot assembly, drill rods, holding dog, circle wrench etc. 整套钻具包括:钻具总成、打捞器、钻杆、绞车、提引器、夹持器及自由钳等部件。