Moed Katan, Chapter 1, Mishnah 6. This Mishnah too deals with matters connected to burial and its preparations on Chol HaMoed.
"Ein chofrin kuchin u'kevaros ba'moed":
One may not dig either kuchin or kevaros on Chol HaMoed. What is the difference between them?
Kuchin - the equivalent of the graves customary among us, digging a grave in the ground.
Kevaros - similar to a grave, except that it involves constructing a structure. It is not clear whether the structure is located within the ground, but in any case it involves building and not merely digging.
Both of these are forbidden on Chol HaMoed.
"Aval mechanchin es hakuchin ba'moed":
The work of "chinuch" is permitted. It means straightening the kuch anew or making adjustments within it - lengthening it slightly or widening it. This work does not involve a great deal of exertion, and therefore it was permitted on Chol HaMoed.
"V'osin nivreches ba'moed":
The nivreches is likewise permitted on Chol HaMoed. Two explanations are given of what it is:
A pit dug in the ground that is filled with water and used for washing clothes.
A sort of bath sunk into the ground, used for preparing bodies for burial - and according to this understanding the matter belongs together with the other topics discussed in this Mishnah.
In any event, this work does not involve exertion and effort to a degree that would justify forbidding it.
Making a coffin in the courtyard of the deceased:
One may make a burial coffin for the deceased in the very courtyard in which the deceased is lying, since then it is evident and clear that the coffin is being made for this particular need alone, and not for some other purpose.
The opinion of Rabbi Yehudah:
Rabbi Yehudah forbids this even in the very courtyard in which the deceased is lying, unless there are boards already prepared with him. In such a case one may join them together on Chol HaMoed, but to begin and prepare the boards from scratch - this is not permitted on Chol HaMoed.
In summary: In this Mishnah we learned that one may not dig kuchin or kevaros on Chol HaMoed, but one may perform "chinuch" on the kuchin and make a nivreches, since these do not involve great exertion. So too, one may make a coffin for the deceased in the very courtyard in which he is lying, for then its purpose is evident; and Rabbi Yehudah forbids even this, unless the boards were prepared beforehand and all the work consists of joining them alone.