Hello,

Basically it's two separate principles involved. The one with an insert of tapering long sides, normally called a wedge where there is a single bearing side which gives its own particular advantages like ease of backing it out for dismantling, for example, but also it can be knocked further in to accommodate expansion and shrinking that might be associated with environmental, lets say seasonal changes or wood drying out. The taper of a wedge is ideally associated with a corresponding opening. The other principle is the peg or parallel sided insert, its advantage being consistent cross-sectional strength across the length, taking both instances relative in nature to each other. In that case the pegs, as Jay writes, are mostly only tapered or pointed on an end to ease entry. My own approach, one I take from my furniture background, is to make pegs longer than you might imagine, twice the length of the beam say, give them a pointed end and then bevel one third of the length, this all normally being then removed and the peg trimmed flush.

Greetings,

Don Wagstaff