This is a mount for attaching a large diameter, light weight Dial Test Indicator to the Creality Ender V3 3D Printer, that bolts directly to the print head mount using two existing 3mm threaded holes.

I used 3mm screws salvaged from old electronics, just make sure they aren't too long. The top one can be 7.5mm from the bottom of the head, but the bottom one needs to be around 6mm long.

The indicator is a Brown and Sharp Best Test. You could use any Dial Test Indicator with a .25" mount.

This is the indicator I used as I already had it in my machine shop. "Brown & Sharpe 599-7031-3 Dial Test Indicator Set, Top Mounted, M1.4x0.3 Thread, White Dial, 0-15-0 Reading, 1.5" Dial Dia., 0-0.03" Range, 0.0005" Graduation, +/-0.0005" Accuracy"
https://www.amazon.com/Brown-Sharpe-599-7031-3-Indicator-Graduation/dp/B0006J4X76/ref=cm_cr_arp_d_product_top?ie=UTF8

Here is a dovetail mount that you can order if you already have a dial test indicator but not a 1/4" mount. "Type Stem For Use With BESTEST Test Indicators Size (Inch) 1/2 (Shank Length) Size (Decimal Inch) 0.250 (Diameter)" https://www.mscdirect.com/product/details/06226757

And a less expensive indicator that comes with a 1/4" mount. "Pro Series by HHIP 4400-0010 Face Dial Test Indicator, 0-.03", White" https://www.amazon.com/HHIP-4400-0010-Indicator-0-03-White/dp/B01BHHXGC8/ref=pd_di_sccai_21?pd_rd_w=8TnLC&pf_rd_p=c9443270-b914-4430-a90b-72e3e7e784e0&pf_rd_r=WP6FJMJRDVMQR1Y5VZ6D&pd_rd_r=1885a9bc-b893-43bc-9704-e53a9e8b33c3&pd_rd_wg=0YkHp&pd_rd_i=B01BHHXGC8&psc=1