Also known as a claquoir. There are MANY variations including one contraption I saw used in Indiana of German design - was like a barrel with a crank. You would crank for the desired duration. Most frequently they are a simple (but beautifully designed / finished) piece of wood with a handle perpendicular on one side, and a rotating arm on the other that swings 180 degrees to clack on both parts of the swing.

In high school, we used a simpler claquoir through the entire year - not to replace the bells as from Holy Thursday Gloria to Holy Saturday Gloria, but to indicate sitting and standing cues. Two clacks = kneel from either sitting or standing. One clack = sit if standing or stand if seated or kneeling. This was a hinged pair of blocks with a little cutout to promote the clack which could be given a precise number of clacks.

The liturgical name is crotalus or strepitus.
https://churchpop.com/2016/03/23/rarest-liturgical-objects-crotalus/

@ Michael: I had seen that article and initially looked for something most similar to the top photo and found this (amazingly expensive) offering for $99 plus recommended $8.95 for faster shipping here Wooden Clacker. But on the lower part of that same article, I saw that "ratchet" type devices were also sometimes used... We are also investigating whether one of our skilled carpenters in the parish could devise something more similar to the claquoir in the top photo. I'll investigate the slapstick option...

It would definitely make it very hard for me to not giggle or eye-roll.
I think that using a slapstick would be a terrible idea.

MO, you are correct as regards the crotalus, but I believe mistaken about strepitus, which refers to the general "earthquake-like" sounds made during the period of darkness in pre-55 Tenebrae when the candle representing Christ (the last one lit) is hidden behind the altar. People bang on the pews, drop books, knock, etc., until the candle is unhidden / unveiled and shines again at which point all noise stops - symbolizing the triumph of Christ over the chaos of darkness.

That is very interesting CC. I wonder if there would be a market for the simple style or crotalus as found in the ebay listing above? That wouldn't take a lot of woodworking skill and seems to be very easy to use, too.

My 91 year old mother was given a wooden clacker by the Pastor of our church many years ago. I cannot ever remember it being used. She was told by the pastor that it was used (Pre Vatican II) instead of bells to indicate the elevation of the Eucharist on Holy Thursday. I was thinking about it the other day and wondering if she still has it. I am surprised to learn that they are still used as part of the Liturgy. It does not look like the ones pictured so perhaps it is for a different purpose. What she has is made of wood. You hold the handle and shake back and forth and a mallet will strike the large oval wooden surface above the handle, first on one side and then the other as you shake hard.

My late father said he used the ratchet-type version as an altar boy 80-85 years ago in a German national parish in Connecticut. My late mother's Irish church up the hill used a wooden clacker in that same period.

This is so very interesting to me... thanks all for the information and comments.

@Liam, this gives me hope that either style will be acceptable for use. I think this is something that will really add something special to the Triduum...

Color me interested. PM me for contact info.

We have and use one. I think it is like yours Francis.

These always gave us choirboys a chuckle at Holy Thursday Mass.

Thank you everyone for this fascinating information. Francis' picture is almost exactly what my mother has. Does it have a Latin name? So am I correct that it was used at Holy Thursday Mass at the elevation of the Eucharist? Is that the only time it would be used?

Used to replace both the sanctus (altar) bell (during the Mass of the Lord's Supper), and the sacristy bell (not for the Good Friday entrance, which is silent, but for the transfer of the Pre-consecrated Sacrament). At least, that's what we did.

Slightly off track, but just noticed that the Missal refers to 'the place of repose'. Does that imply that the Blessed Sacrament should remain in the church (in a tabernacle) on the altar to which it was transferred, throughout the time from Watching on Holy Thursday to the Communion on Good Friday? That's not what I have seen in the last forty years.

We also use them at our Basilica.

(I don't remember that always being the case, but I also remember a limited use of Sanctus bells with our previous pastor, anyway. )

Slightly off track, but just noticed that the Missal refers to 'the place of repose'. Does that imply that the Blessed Sacrament should remain in the church (in a tabernacle) on the altar to which it was transferred, throughout the time from Watching on Holy Thursday to the Communion on Good Friday? That's not what I have seen in the last forty years.

That's exactly how we do it. The time between Thursday and Friday is a time for silent adoration at the side altar where the portable tabernacle is located.

We use them from after the Gloria on Holy Thursday until the Gloria of the Easter Vigil. The tower bells are also silent during the Triduum.

building the prototype of Crotalus now

btw... can also make Tenebrae Candlestand

This is my latest sculpture which is also for sale:

http://tetoncraftworks.com/sacred-icon

Also interested in the candlestand for next year!

You wouldn't also be able to help construct a catafalque, would you?

They're routinely used in solemn EF celebrations for All Souls Day.

On second thought ... maybe it was Rossini????

https://www.youtube.com/watch?v=U3nIScO592Y

The strepitus is used at Walsingham, and, I would presume, throughout the Ordinariate.
That there should be a place in which it is not used seems highly eccentric to me.

A 'thunder sheet', eh?
How droll.

Stimson in Rehab. My initial idea is one where I would carve four angels at each corner holding up the deceased.