As I have mentioned in the comment, I personally have been told to use the Mudra (shown in the video) while invoking my Guru before starting daily practice etc. I have been told it's called the Mrugi Mudra to be formed at the top of the head, the place the Guru is said to be situated.
I was able to find a reference from the article "shrIvidyA upAsanA tattva" hosted @Kamakotimandali:
The first qualification for a Upasaka to perform Pooja is obtaining
Diksha from a competent Guru. the rite called Diksha is supposed to be
destroying all the limiting factors of the individual self and
facilitate his union with Shiva.
aIyate shivasAyujyaM kShIyate pAshabandhanam |
atha dIkSheti kathitaM
budhaiH sacChAstravedibhiH ||
It is the Guru who, after testing the disciples competence, initiates
him into the Upasana by teaching him the mantra, the Devata Swaroopa
and the methods of performing the rituals. Though the Sadhaka begins
initially with external rituals, he should rise to the level of
performing Antaryaga as set out in Bhavanopanishad. The first step in
Bahiryaga is the method of entering the room of worship. Next follows
Tatva Achamana. This is a cleansing process carried out by ingesting
drops of water four times or seven times, praying each time for the
cleansing of the Anava, Mayika and Karmika Malas, which is
accomplished by the usage of Bija mantras. This prepares the Sadhakas
mental frame and sets it ready for the Jnana swaroopa to shine.
The next and the most important step is performing GuruPaduka Vandana. This involves paying one's respect to the lotus feet of the
Guru. There is a special prescribed procedure for performing this.
Guru's feet are supposed to be on the head of the Upasaka. Therefore,
he has to worship with his hands locked in Mrigi Mudra, the sandals
of the preceptor. This procedure calls for worshipping his own master
(Guru), the Guru's Guru (Parama Guru) and his Guru (Parameshthi Guru).
There are three separate mantras for each of these. The GuruPaduka
mantras collectively connote the same concept as that of the Mahavakya
Tatvamasi. Actually, these syllables are represented one each by the
three Paduka mantras.
As per the article, it's done while performing the Guru Paduka Puja. Guru Paduka (Sandals of the Guru) has to be imagined to be situated at the top of the disciple's head. That's why the Mudra has to be shown/formed at the top of one's head.