measure

We bought a new build..... We believe the front door and one internal wall are not straight how would I measure the deviations? Is it just case of a piece of string and measuring the gap between one end and another? Or are there easier ways?

Hi. Thanks for holding these forums. Does anybody know, please, how to measure for a roof ladder or what the length dimension of for example a roof ladder Lyte 155 21 rung 5.46m ladder refers to so that I can judge the length against my roof? Should the ladder over hang at all or end just on...