Usually a good tape will work.
But sometimes a calpier is easier to use.
There are many expensive ones.
But the inexpensive plastic alternatives can be useful.
They are easy to carry and can be shared or lent with no worries.
I have purchased them for less than 1.00
Step 1: Check the Thickness of a Piece of Plywood
The cali[per shows it a little thinner; it is an inexpensive one
Step 2: Check the Outer Diameter of a Strainer
It is a 2 1/2 inches
Step 3: Check the Inner Diameter of a Strainer
A pipe would be a more typical object
It is 2 1/18
Step 4: So Get Some Calipers
If you do not, get some cheap ones.
They do come in handy.