# Masks In same modules you can specify a symbol masks how source. This build from standard charsets: * ?l — all letters of english alphabet, lower case * ?u — all letters of english alphabet, upper case * ?d — all digits Charset ?s not using because this symbols not using in domain or directory names. You can specify two types of masks. Simple mask with specify every symbol. For example «?l?l?d?d» - it mean all phrases with length 4 symbols and where first two symbols - all letters of english alphabet in lower case, and second two symbols — all digits. Mask with length range. For example «?l?d,1,4» - all phrases with length from 1 to 4 symbols, contains all letters of english alphabet in lower case and all digits. --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://webscout.gitbook.io/webscout-en/masks.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.