*** no personal or business checks accepted without Bank Letter ***
Sample Bank Letter ---

On the Bank's Letterhead - addressed to Bevco Auctions
{Bank Name} will guarantee payment on checks written by {Customer Name} 
on account (Account Number}, not to exceed an aggregate amount of {Specific $$ Amount}
for the purposes of making purchases at

Auction of January 26th, 2019 
{Customer Name} understands that no Stop Payment orders will be placed or honored on these funds.
Must be signed by Bank Officer and include title and phone number.