Mold-blown goblet of bluish-green glass with pronounced vertical ribs. Its spun foot is followed by a tall straight stem, which is slightly constricted where a spun collar was applied, and a globular bowl with a narrow, straight-sided rim.

Some of the drinking glasses made in northern forest glasshouses were large and elaborate. The Knotsbeker is a variation of the Keulenglas (club-shaped beaker), a straight-sided vessel with a bulging wall that narrows slightly near the rim. The largest of these glasses were 30 to 50 centimeters tall and held half a liter of beer. Smaller examples were used for wine. Such glasses were popular during the second half of the 15th century, but they had disappeared before the end of the 16th century. The Knotsbeker illustrated here is an extremely rare and luxurious form of forest glass. Beakers of this type, but without the trailed collar around the stem, have been found in the Netherlands and northern France.