Help needed with a bolts name

Im beginning to make a bunch of tables and chairs for a new customer. They are fairly simple in design, but I wish to flat pack them.



I can't remember the name of the bolt system, but one drills a hole and using an Allen key, a "pre bolt" is screwed into the brace or skirt The bolt that passes through the leg then screws solidly into that.



I'm not sure what its called, so I can't find a picture to even show what I'm talking about!



More description: let's say, rather than using a lag bolt with a course thread that drills directly into the timber, a two-part bolt system is used. A hole is drilled, say 8mm, into that is screwed a lug. This lug has very coarse threads on the outside, it grips into the timber. The inside has a fine thread. The bolt would pass through the leg of a chair or table, then the fine screw would engage the lug and it would be wound tight using an Allen key too.



I'd imagine such a system would be used on consumer knock down furniture like tables and beds.



Any help with what they are called and/or a good supplier would be an added bonus.



Thanks all!