<s>[INST] Why are certain types of door locks called 'deadbolts' ? [/INST] A deadbolt can only be opened by a key or handle, while the more common spring bolt uses a spring to hold the bolt in place, allowing retraction by applying force to the bolt itself. 
A deadbolt is therefore more resistant to being forced open and is usually used in combination with to a spring bolt lock on doors for additional security.</s>\ <s>[INST] What is the highest selling deadbolt lock in 2020?  Who manufactured it?  What city has the highest concentration of deadbolt users?  Is their a correlation to deadbolt usage and crime? [/INST] 