Some students need to be explicitly taught and encouraged to request help on a task due to social/emotional or learning issues. These "tickets" serve as a visual reminder -- to help students develop the ability to self-assess their learning and think about how much they understand.
Print (and laminate if desired) these tickets on card stock paper. Pre-teach and discuss with student(s) the purpose of this visual aid (to help you think about how much you understand and if you need help). The more students are able to articulate and explain their thinking, the better we are supporting their meta-cognitive skills (e.g., I understand the 1st part but then I'm confused with the next step).
These work well for multi-step directions during independent work, math word problems, new activities, reading comprehension questions, etc.
Keep on students' desks, tables or use as bookmarks.
Consider making this a whole class goal- to articulate and explain what we don't understand (e.g., We usually know when we don't understand something, but let's all work on identifying which part, or how much we don't understand so I am better able to help you.).