the slot for supplying a liquid finish to the slot more particularly the passage 30 extends through the bottom wall 28 and through a portion 24a 26a of each side wall 24 26 adjacent the bottom wall portions 24 a and 26 a thus become extensions of passage 30 the cross sectional area of each side wall portion of passage 30 generally does not exceed 25 percent and must be at least 15 percent of the cross sectional area of the passage 30 where it extends through the bottom wall the yarn 11 runs from top to bottom of the applicator as indicated by the arrow as best seen in fig2 4 the slot 20 is defined by side walls 24 26 and a bottom wall 28 the side walls 24 26 taper inwardly toward each other as they approach bottom wall 28 and also taper toward each other as they progress from top to bottom of the applicator body member the configuration of the slot 20 is a critical feature of the invention more particularly the slot is tapered where the filament bundle of the moving yarn line 11 contacts the bottom wall 28 finishing liquid is applied to the yarn at the initial point of contact with the bottom and or side walls of the slot as the case may be i e at passage 30 in operation the yarn picks up finish at the point of initial yarn contact with the bottom wall or side walls of or both of the slot depending on threadline alignment in the slot.