An insert is commonly known as the substitution of the part in wood known as the neck. It goes from the dovetail, that is to say, the carving where the higher stock is slotted in, to the jaws, the lateral parts of the pegbox. In ancient double-basses, the insert was common practice, aimed at enhancing the instrument, adjusting it to the right proportions with the board, whereas the neck was not proportioned to it. Sometimes the substitution is necessary due to the presence of woodworm and to evident breakages. In the past when the curl broke the luthier would re-build both the neck and the curl. This is why the curls we find today on many ancient instruments are not original. Luckily enough, during the last years, the restoration has tended to maintain the original features of the instrument. Let us get down to practical matters. First, remove the fretboard and saw through the old neck, removing the wood inside the stock and being careful not to damage the nut (unfortunately, in this instrument, the nut had already been damaged) and the curl. Secondly, choose a block of highly-seasoned maple wood (at least 7 years old) with straight and thick fibres while the marbling can be according to your personal taste. Then, decide how much weight to charge on the sounding board (this is the most important operation, showing the degree of experience by the luthier), the height of the bridge, by keeping in mind:

• the thickness of the board (we can measure them even without opening the instrument)
• the veining of the wood
• the dimension of the chain
• the bulging
• the width of the central part of the board

After deciding the height of the bridge, it is necessary to calculate the proper neck length (see Xbass.org No.3). Measure it with a semi-movable system that will calculate the proper inclination and mark the points on the block with a pencil. Then, place the curl in line with the neck. The scroll shall be inserted in line with the edge of the sounding board, at the end of the dovetail with the bridge exactly in the centre. The bayonet insert must be perfect, with every part fitting perfectly, respecting the measures of the position of the nut. Now, stick and re-make the board by adjusting the edges. Prepare the lower part for the insertion of the dovetail and, before the final sticking, check that everything is ok. Stick, polish and adjust the edges, the fretboard, the bridge and the varnish. Your work is done!