We can still do it
In 1999, Timmerfabriek Gebr Bos was the first joinery in the Netherlands to obtain the KOMO approval with product certificate for round frames. These days, round frames are primarily used in more specialised building objects in the utility, restoration and special home sectors. This applies to classic building styles and ultra modern buildings alike. The round frames can be fitted with either a pivot or a hopper window. Semi-manufactured individual curved sills are also available.