Double fillet weld symbol

A double fillet is not a special symbol. It is the ordinary fillet triangle used twice on one reference line, once below for the arrow side and once above for the other side. Both refer to the same joint that the single arrow points at, so you never need a second arrow or a second symbol to call for welding both faces of a tee or a corner.

Read each triangle completely on its own before comparing them. Take the size from the left of that triangle, the length and pitch from the right of it, and the contour from beyond its outer face. Only then look at whether the two match. Symmetric double fillets are the common case, but a heavier weld on one face is perfectly normal where loading or access differs side to side.

The doubled symbol is the workhorse of structural fabrication because a fillet on each face roughly doubles the joint's shear capacity while keeping preparation at zero — no bevelling, no root opening, just two surfaces brought together and welded. It also balances shrinkage across the joint, which keeps the upright member from pulling toward the welded side.

Sequence is not part of the symbol. If the order matters — for instance alternating passes side to side to control distortion on a long member — that has to come from a note, the tail, or a written procedure. Reading a double fillet symbol tells you what to deposit, never in what order to deposit it.