Special Unicode Characters in Data Validation Lists: ☐, ☑, ✓, ✔ - This may be my favorite approach. You can include special characters like this in a Data Validation drop-down list. This isn't quite as good as clicking once to fill in a checkbox, but it is great for the mobile Excel apps. The only hard part is remembering how to insert a check mark symbol in Excel. For more information, see my article Using Unicode Character Symbols in Excel.
Photography websites might encourage a monthly membership because it wants to reward its photographers for sharing their hard work with others, whilst others might want to create and launch online courses and offer them through membership options, without having to spend a specific amount of money to purchase and use. The capabilities of membership sites are big, and sometimes what we need not a good idea but a good membership site software to help us build the kind of site we are looking to build.
In professional diving, checklists are used in the preparation of equipment for a dive, and to ensure that the diver and life support systems are fully prepared before they enter the water. To a lesser extent, checklists are used by a minority of recreational divers, and by a larger proportion of technical divers during pre-dive checks. Studies have shown checklists to be effective at reducing the number of errors and consequent incidents.