Full step by step instructions here; https://scantoweb.net/check-out-and-check-in/
Using barcodes and a little creating spreadsheet formula; you can have a powerful Google Sheets based check in and out process.
Create barcodes; scroll down on this page for the Google Sheets formula.
https://berrywing.com/barcode/
Formulas;
=IF(ISBLANK(CHECKEDOUT),"--NA--", IF(COUNTIF(SCANNEDIN, CHECKEDOUT)=0, "OUT: "&CHECKEDOUT & " STILL OUT " & OUTWHO,CHECKEDOUT&" IS IN"))